Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1985-1989  (43,497)
  • Chemistry  (41,782)
  • Atomic, Molecular and Optical Physics  (1,119)
  • Life Sciences (general)  (596)
Source
Material
Years
Year
Keywords
  • 101
    Electronic Resource
    Electronic Resource
    Vibrational CD studies of the solution conformation of simple alanyl peptides as a function of pH (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 2025-2044 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The CH-stretching vibrational CD (VCD) spectra of glycyl-L-alanine, L-alanylglycine, and L-alanyl-L-alanine have been studied at neutral, high, and low pH in D2O solution. The intense positive VCD band attributed to the CαH stretch of the alanyl residue in glycyl-L-alanine at neutral pH is absent in L-alanylglycine. In contrast to the VCD spectra of L-alanine, the positive methine-stretching VCD band in glycyl-L-alanine and L-alanyl-L-alanine is still present at pH 2. Based on the ring current mechanism, the VCD spectra are consistent with the presence of a five-membered CO … HN intramolecular hydrogen-bonded ring between the C-terminal carboxylate and peptide NH groups at neutral and high pH, and a seven-membered COH … O=C hydrogen-bonded ring between the C-terminal carboxyl OH and peptide C=O groups at low pH. In the N-terminal alanyl residue, the peptide C=O group is hydrogen bonded to the NH trans to the methine bond. The CH-stretching VCD spectra of L-alanyl-L-alanyl-L-alanine at neutral pH are consistent with two intramolecularly hydrogen-bonded conformations for the central alanyl residue.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281116
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 102
    Electronic Resource
    Electronic Resource
    Ir vibrational CD in model deoxyoligonucleotides: Observation of the B → Z phase transition and extended coupled oscillator intensity calcuations (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 2047-2058 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first observation of ir vibrational CD (VCD) in small model DNA molecules is reported. The VCD signals in the 1550-1750-cm-1 spectral region, which originate from coupling of carbonyl stretching modes of the nucleic acid bases, are found to be sensitive to the handedness of the polymer helix.The formalism to calculate VCD intensities of polymers is developed from the exciton model derived earlier by Tinoco [(1963) Radiation Res. 20, 133; (1960) J. Chem. Phys. 33, 1332; (1964) J. Am. Chem. Soc. 86, 297] and Schellman and co-workers [(1975) Biopolymers 14, 173; (1969) J. Phys. Chem. 73, 28]. The resulting equations, which are a direct extension of the dimeric case known as the “coupled oscillator,” are used in model calculations of the helical polymers.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281202
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 103
    Electronic Resource
    Electronic Resource
    Unusual condensation behavior of poly(dA)-poly(dT) (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1645-1650 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280913
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 104
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281001
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 105
    Electronic Resource
    Electronic Resource
    Theory of cooperative transitions in protein molecules. II. Phase diagram for a protein molecule in solution (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1681-1694 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermodynamically stable states of denatured protein in solution are investigated. These states are distinguished from the native state by the absence of tight packing of side chains while the compactness of denatured protein may vary within a wide region. The following regimes are outlined: 1the “wet” molten globule, i.e., the compact state with pores occupied by solvent;2the swollen globule (“wet,” of course); and3the coil.The “dry” molten globule, when solvent does not penetrate inside the protein, is excluded for all experimental conditions. All the transitions within the denatured globule state are gradual while the denatured globule-coil phase transition is a second order one. The conditions of protein denaturation as well as conditions of transitions and crossovers within the denatured state are outlined.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281004
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 106
    Electronic Resource
    Electronic Resource
    Allosteric formulation of thermal transitions in macromolecules, including effects of ligand binding and oligomerization (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1705-1729 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We examine the effects of concentration (aggregation), buffers, and ligation, under conditions of either constant ligand activity or limited total amount of ligand, upon thermal denaturation of macromolecules as measured by scanning calorimetry. In doing so we utilize and extend an earlier generalized allosteric treatment [S. J. Gill, B. Richey, G. Bishop, and J. Wyman (1985) Biophys. Chem. 21, 1-14], applicable to ligand binding, enthalpy changes, and volume changes in a macromolecular system. The approach is contrasted with formulations based on the idea of structural domains. We show how information from the full scanning calorimetric curves can be utilized in arriving at and testing appropriate models for observed behavior in selected examples.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281006
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 107
    Electronic Resource
    Electronic Resource
    Inverted repeat sequences can influence the melting transitions of linear DNAs (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1745-1758 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of inverted repeat sequences on the melting transitions of linear of DNAs has been examined. Derivative melting curves (DMC) of a 514 base pair (bp) DNA, seven subfragments of this DNA, and four other DNAs have been compared to predictions of DNA melting theory. The 514-bp DNA contains three inverted repeat sequences that can form cruciform structures in supercoiled DNA. We refer to these sequences as c-inverted repeats. Previous work showed that the DMC of this DNA, unlike a number of other DNAs, is not accurately predicted by DNA melting theory. Since the theoretical model does not include hairpin-like structures, it was suggested that hairpin or cruciform formation in these inverted repeats may be responsible for this discrepancy. Our results support this hypothesis. Predicted DMCs are in good agreement with DNAs with no inverted repeats, or inverted repeats not evident in supercoiled DNA. Differences between the theoretical and experimental Tm's are ≤ 0.3°C. DNA molecules that contain one or more of the three c-inverted repeats are not as accurately predicted. Experimental Tm values are lower than predicted values by 0.7-3.8°C. It is concluded that some inverted repeat sequences can form hairpin-like structures during the melting of linear DNAs. These structures appear to lower overall DNA stability.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281008
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 108
    Electronic Resource
    Electronic Resource
    The biased reptation model of DNA gel electrophoresis: Mobility vs molecular size and gel concentration (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1781-1791 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The biased reptation model provides a good framework for interpreting the results of continuous field DNA electrophoresis experiments performed in agarose gels. Here we discuss the main features of the mobility-molecular size and mobility-gel concentration diagrams as obtained from new extensive computer simulations of the model. Our aim is to suggest a global and coherent picture of this widely used yet poorly understood experimental technique, and to point out the areas where a systematic experimental study is still needed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281011
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 109
    Electronic Resource
    Electronic Resource
    DNA backbone flexibility and the Z access for phosphodiester linkage: A quantum molecular approach (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1827-1831 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281014
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 110
    Electronic Resource
    Electronic Resource
    Linear dichroism studies of the complexes between CT-DNA and distamycins (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 2177-2194 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The study of the monomeric chromophore of the distamycins reported in Ref. 1 was used here to build up a description of the electronic states of the whole oligopeptide by the exciton theory. Liquid crystal-linear dichroism (LC-LD) spectra of the distamycins were recorded by using as orienting solvents both thermotropic and lyotropic mesomorphic media. The agreement between the LD spectra and the polarization assignments by the exciton treatment is satisfactory. On this basis the flow-LD spectra of the complex between distamycin V and DNA was interpreted in terms of the preferred relative orientations of the guest and host molecules. A single site location of the distamycin within the minor groove does not perfectly match the experimental order parameters. This orientational distribution function could be too simple to explain the experimental data. It may therefore be assumed that a small fraction of the guest molecules are preferentially aligned more parallel to the host chain axis than the minor groove. Alternatively, and probably more likely, the partial mismatch of the experimental data with the minor groove location may be seen as a manifestation of the well-known stiffening and bending effects at the binding sites, which have already been observed by other techniques.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281210
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 111
    Electronic Resource
    Electronic Resource
    Characterization of the reaction products of adult human hemoglobin and disuccinimidyloxalatethe opinions or assertions contained herein are the private views of the authors, and are not to be construed as official or reflecting the views of the department of the army or the department of defense. (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 2195-2200 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of chemically modified hemoglobin preparations have been proposed for use as an emergency resuscitation fluid. The purpose for forming these hemoglobin derivatives is to decrease the oxygen binding (i.e., to increase the P50) and to increase the intravascular retention time. These goals have been met with various degrees of success by using the reaction with pyridoxyl 5-phosphate to raise the P50, followed by the addition of glutaraldehyde to increase circulating half-life by polymerization.1,2 Other derivatives have been formed with polyethylene glycol,3,4 bis-(3,5-dibromosalicyl) fumarate,5,6 glycolaldehyde,7 and 2-nor-2-formylpyridoxal 5-phosphate,8,9 as well as with other compounds. All these derivatives introduce a foreign molecule into the hemoglobin, which may not always be desirable. Recently Tharp and Day10 used cyanogen to form intersubunit amide cross-links in hemoglobin without the incorporation of cyanogen. This approach is attractive if the appropriate functional properties can be attained. Takeda et al.11 showed that equimolar concentrations of amino acids and disuccinimidyloxalate could form peptide bonds in high yield. We report the characteristics of the hemoglobin molecule modified by internal covalent amide bonds, which may be a suitable candidate for a resuscitation fluid.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281211
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 112
    Electronic Resource
    Electronic Resource
    Mechanische eigenschaften von polyesterfasern bei kurzzeitiger beanspruchung, 3Teil 2: cf. Lit.1.. Konstruktion von relaxations- und retardations-masterkurven von polyester-multifilamentgarn (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 1-15 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polyethylene terephthalate (PETP)-multifilament yarns with different thermal history were used as testing materials. Stress-strain-curves from 0.1 up to 100000%/s were determinated. These data were used to compute relaxation- and retardationcurves over 7 decades of time. By superponing relaxation-functions for various elongations respectively retardation-functions for various stresses, mastercurves over 21 respectively 13 decades of time were obtained which can be subdivided into 4 regions, associating the following changes of structure: Region 1: suddenly recovering quasielastic deformation with relaxation times between minor 1 and 10 sRegion 2: irreversible deformation, consolidation, with relaxation times between 10 and 105 s,Region 3: elastic behaviour of the physical network with relaxation times between 105 and 107 s andRegion 4: transformation and destruction of the network with relaxation times between 107 and 1016 s.
    Notes: Von Polyethylenterephthalat (PETP)-Multifilamentgarnen mit unterschiedlicher thermischer Vorgeschichte wurden Kraft-Dehnungs-Kurven mit den Dehngeschwindigkeiten 0,1 bis 100 000%/s ermittelt. Diese lassen sich zu Relaxations- und Retardationskurven über sieben Zeitdekaden umrechnen. Durch Superponieren von Relaxationsfunktionen für unterschiedliche Dehnungen bzw. Retardationsfunktionen für unterschiedliche Fadenzugspannungen werden Relaxations- und Retardationsfunktionen bis 21 bzw. 13 Zeitdekaden bestimmt, die sich in vier Bereiche unterteilen lassen, denen folgende Strukturveränderungen zugeordnet werden können: Bereich 1: sofort erholbare, quasielastische Deformation mit Relaxationszeiten kleiner 1 bis 10 s,Bereich 2: irreversible Deformation, Verfestigung, mit Relaxationszeiten zwischen 10 und 105 s,Bereich 3: elastisches Verhalten des physikalischen Netzwerkes mit Relaxationszeiten zwischen 105 und 107 s undBereich 4: Umbau und Zerstörung des Netzwerkes mit Relaxationszeiten zwischen 107 und 1016 s.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690101
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 113
    Electronic Resource
    Electronic Resource
    Mechanische eigenschaften von polyesterfasern bei kurzzeitiger zugbeanspruchung, 4Teil 3: cf. Lit.10.. Strukturveränderungen durch kurzzeitverformung an polyester-monofilamentgarn (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 17-27 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Interferometric measurements of a PETP-monofilament yarn show that the orientation of the high pre-orientated material decreases after stretching and relaxing. The effect of desorientation is more distinctive by a slower deformation then by a high-speed deformation. The lower decrease is caused by a slower deformation. Material strained with a rate of 104%/s shows “crazes” visible by interferometry. These “crazes” are not cracks but sites with lowered orientation. For slower deformation it is visible interferometrically that the orientation of the macromolecules in the fiber is asymmetric. DTA-curves from PETP-fibres show an exothermic peak between 30 and 80°C which can be related to specific structures of the non cristalline regions. By low-speed straining this peak shifts to lower temperatures. Stress-free storing of the material causes the peak to move back to the original temperature. For material deformated at high-speeds this peak does not change its position.
    Notes: Interferenzmikroskopische Messungen eines PETP-Monofilamentgarns zeigen, daß die Orientierung des schon hoch vororientierten Materials durch Dehnen und wieder Entspannen abnimmt, langsame Verformung wirkt dabei stärker desorientierend auf das Material als eine schnelle Verformung. Die Packungsdichte nimmt durch Dehnen ab. Die größte Dehngeschwindigkeit bewirkt die größte Abnahme.Ein mit der Dehngeschwindigkeit ∊ = 104%/s gedehntes Monofilament zeigt interferenzmikroskopisch sichtbare „Crazes“. Diese „Crazes“ sind keine Risse, sondern nur rißförmige Orte verminderter Orientierung. Für kleinere Dehngeschwindigkeiten ist interferenzmikroskopisch Unsymmetrie der Orientierung sichtbar. DTA-Kurven von PETP-Fasern zeigen zwischen 30 und 80°C einen exothermen Peak, der spezifischen Strukturen der fehlgeordneten Bereiche zugeordnet werden kann. Bei niedrigen Dehngeschwindigkeiten verlagert sich dieser Peak zu niedrigeren Temperaturen. Durch Lagern des Materials kehrt er zur ursprünglichen Temperaturlage zurück. Für schnell deformiertes Material ändert dieser Peak seine Temperaturlage nicht.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690102
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 114
    Electronic Resource
    Electronic Resource
    Organotin polymers XIVPart XIII cf. Acta Polym. 11 (1988) 645.. Synthesis and copolymerization reactions of p-acryloyloxy-tri-n-butyltin benzoate with some vinyl monomers (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 59-68 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: p-Acryloyloxy-tri-n-butylzinnbenzoat (ABTB) wurde durch Reaktion von p-Hydroxy-tri-n-butylzinnbenzoat und Acrylsäure in Gegenwart von Dicyclohexylcarbodiimid hergestellt. Die Monomerreaktivitätsverhältnisse für die Copolymerisationen von ABTB (M1) mit Methylacrylat (M2), Ethylacrylat (M2), n-Butylacrylat (M2), Methylmethacrylat (M2), Styrol (M2) und Acrylnitril (M2) wurden entsprechend zu r1 = 0,080, r2 = 1,046; r1 = 0,039, r2 = 1,585; r1 = 0,019, r2 = 2,076; r1 = 0,150, r2 = 1,710; r1 = 0,113, r2 = 1,339 und r1 = 0,007, r2 = 2,853 bestimmt. Die Q- und e-Werte für das zinnorganische Monomere wurden berechnet. Die Copolymerisationen wurden in Lösung bei 70°C mit 1 mol-% Azobisisobutyronitril als Initiator durchgeführt. Die Struktur von ABTB und der hergestellten Copolymeren wurde durch IR-und 1H-NMR-Spektroskopie untersucht.
    Notes: p-Acryloyloxy-tri-n-butyltin benzoate (ABTB) was prepared by the reaction of p-hydroxy-tri-n-butyltin benzoate and acrylic acid in the presence of dicyclohexylcarbodiimide. The monomer reactivity ratios for the copolymerizations of ABTB (M1) with methyl acrylate (M2), ethyl acrylate (M2), n-butyl acrylate (M2), methyl methacrylate (M2), styrene (M2) and acrylonitrile (M2) have been found to be r1 = 0.080, r2 = 1.046; r1 = 0.039, r2 = 1.585; r1 = 0.019, r2 = 2.076; r1 = 0.150, r2 = 1.710; r1 = 0.113, r2 = 1.339 and r1 = 0.007, r2 = 2.853, respectively. The Q and e values for the prepared organotin monomer were calculated. Copolymerization reactions were carried out in solution at 70°C using 1 mol-% azobisisobutyronitrile. The structure of the ABTB monomer and the prepared copolymers was investigated by IR and 1H-NMR spectroscopy.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690106
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 115
    Electronic Resource
    Electronic Resource
    Application of a mathematical model for the polyesterification process based on mixtures of fumaric acid and adipic acid without catalyst (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 49-58 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die Herstellung von ungesättigten Polyestern untersucht, die aus Mischungen von Fumarsäure und Adipinsäure in verschiedenen Verhältnissen ohne zusätzlichen Katalysator entstehen. Der Verlauf der Polyveresterung wurde durch die Bestimmung der während der Reaktion produzierten Wassermenge verfolgt. Die kinetischen Parameter der Polyveresterung (Reaktionsordnung n, Aktivierungsenergie E, Frequenzfaktor k0) wurden bestimmt, und es wurde n = 3 in allen Fällen festgestellt, während die Werte von E und k0 mit zunehmendem Fumarsäureanteil in der Anfangsmischung zunehmen. Ein mathematisches Modell für die Polyveresterung wurde bestimmt, was auf den Herstellungs-Parametern (z. B. Aufheizprogramm) und den kinetischen Parametern basiert, und es wurde festgestellt, daß die Korrelation zwischen den Kurven der experimentell entstandenen Wassermenge und der theoretischen (berechneten) Wassermenge sehr gut ist. Die Eigenschaften der Endprodukte, wie Viskosität und die schwach gelbe Farbe, nehmen mit zunehmendem Fumarsäureanteil in der Anfangsmischung zu. Es wurden auch generelle Perspektiven für die praktische Anwendung dieser Methode diskutiert.
    Notes: The production of unsaturated polyesters based on mixtures of fumaric acid and adipic acid for different proportions without added catalyst was studied. The progress of the polyesterification was followed by determining the amount of water produced during the reaction. The kinetic parameters (reaction order n, activation energy E, frequency factor k0) of the polyesterification were determined and it was found out that n = 3 in all cases, while E and k0 increased by increasing amount of fumaric acid in the initial mixture of the reaction. A mathematical model for the polyesterification based on the production parameters (e.g. the heating program) and on the kinetic parameters was used and very good correlation was found between the corresponding pair of curves of water produced during the polyesterification, which were determined experimentally and theoretically (by calculating). With regard to the properties of the final product it was found out that its viscosity and its slight yellow colour increased by increasing the amount of fumaric acid in the initial mixture of raw materials. General prospects for practical application of this method were also discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690105
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 116
    Electronic Resource
    Electronic Resource
    Synthesis and impact behaviour of PMMA/EVA interpenetrated blends (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 137-143 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die vorliegende Arbeit untersucht das linear-elastische Bruchverhalten von (PMMA) mit Poly(ethylen-co-vinylacetat) (EVA) oder EVA  -  g-Bernsteinsäureanhydrid (EVA-g-SA) mittels Kerbschlagzähigkeitsmessungen nach Charpy. Rasterelektronenmikroskopaufnahmen zeigen, daß in Blends, die durch „in situ“-Polymerisation des acrylischen Monomeren in Gegenwart des Elastomeren hergestellt wurden, eine IPN-Morphologie vorliegt, während ein Blend, das durch Mischung der Polymerkomponenten im Schmelzezustand gebildet wurde, die typische zweiphasige Struktur von dispergierten Elastomerdomänen in einer glasartigen Matrix zeigt.Die Ergebnisse der mechanischen Messungen stimmen gut mit den beobachteten Morphologien überein.
    Notes: In the present work blends between poly(methylmethacrylate) (PMMA) and poly(ethylene-co-vinylacetate) (EVA) or its derivative EVA-g-succinic anhydride (EVA-g-SA) have been investigated by linear elastic fracture mechanics (LEFM) with Charpy impact tests and by scanning electron microscopy (SEM). Blends prepared by “insitu” radical polymerization of the acrylic monomer in the presence of the rubbers have an IPN morphology, while a blend prepared by melt-mixing the polymer components shows the typical biphasic structure of rubbery domains dispersed in a glassy matrix.Furthermore, a different behaviour is found when using EVA-g-SA instead of EVA. A fair agreement is found between the response of the LEFM analysis applied to the results of Charpy impact tests and the observed morphologies.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051700110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 117
    Electronic Resource
    Electronic Resource
    Synthese verschiedener Oxincellulosen für spurenanalytische Anreicherungsverfahren (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 159-172 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Some routes to synthetize covalently bound chelating groups as 8-hydroxyquinoline or 8-hydroxyquinoline-5-sulfonic acid to cellulose are given. The products show a capacity of 500-800 μmol/g, fast kinetics of exchange and good stability against the eluent. The apparent stability constant of the complexes with Zn2+ are around 2 · 105 mol-1 dm3.
    Notes: Es werden mehrere Synthesemöglichkeiten für die Herstellung von an Cellulose immobilisierten 8-Hydroxychinolin- und 8-Hydroxychinolin-5-sulfonsäure-Derivaten beschrieben, die zu einem Produkt mit einer Kapazität von 500-800 μmol/g, hoher Austauschgeschwindigkeit und guter Stabilität gegenüber dem Eluenten führen. Die scheinbare Komplexbildungskonstante der Oxincellulosen mit Zn2+ ist etwa 2 · 105 mol-1 dm3.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051700112
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 118
    Electronic Resource
    Electronic Resource
    Oberflächenstrukturierung polymerer Fasern durch UV-LaserbestrahlungTeil 3 cf. Lit.2.. 4. Der Einfluß äußerer Spannungsfelder (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 203-210 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: This paper reports the results of UV-laser-irradiations of elastomer fibres under application of varying external tensions on the fibres and under varying laser conditions. It is known that tension as well as temperature fields can lead to these synergetic effects that are supposed to cause the surface structuring by UV-laser-irradiation. Therefore the purpose of the reported experiments was to evaluate whether tension or temperature as the source of the system instabilities eventually lead to surface structuring.
    Notes: Dieser Beitrag berichtet über die UV-Laserbestrahlung von Elastomerfasern unter dem Einfluß verschieden großer äußerer Spannungsfelder und unterschiedlicher Laserbedingungen. Aus der Literatur ist bekannt, daß synergetische Effekte, die als Ursache der Oberflächenstrukturierung angesehen werden, sowohl durch Temperaturwie auch Spannungsfelder getrieben sein können. Daher sollen die beschriebenen Experimente untersuchen, welche der genannten Bedingungen in der Hauptsache zur Instabilität des Systems und damit zur Oberflächenstrukturierung führen.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051700116
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 119
    Electronic Resource
    Electronic Resource
    Crosslinking of polyethylene photoinitiated by benzoquinones and naphthoquinones (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 173 (1989), S. 47-53 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die Vernetzung von Polyethylen mit Benzo- und Naphtochinonen als Photoinitiatoren untersucht. Die Quantenausbeuten (ϕ) der Initiatorreaktionen in Polyethylen unter UV-Bestrahlung wurden gemessen. Die ϕ-Werte für Benzochinon, Tetrachlorbenzochinon, Tetrabrombenzochinon, Tetrafluorbenzochinon, Naphthochinon und 2,3-Dichlornaphtochinon waren 0,23, 0,18, 0,14, 0,26, 0,09 bzw. 0,11. Naphthochinone waren als Initiatoren zur Photovernetzung von Polyethylen effektiver.
    Notes: Crosslinking of polyethylene (PE) photoinitiated by some benzoquinones and naphthoquinones has been studied. The quantum yields (ϕ) of the initiator reactions in PE under UV irradiation were measured. The ϕ-values for benzoquinone, tetrachlorobenzoquinone, tetrabromobenzoquinone, tetrafluorobenzoquinone, naphthoquinone, and 2,3-dichloronaphthoquinone were equal to 0.23, 0.18, 0.14, 0.26, 0.09, and 0.11, respectively. Naphthoquinones were more effective as initiators in photocrosslinking of polyethylene.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051730104
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 120
    Electronic Resource
    Electronic Resource
    Modification of wood fiber surface by grafting and its effect on mechanical properties of polystyrene filled system (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 173 (1989), S. 101-110 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polystyrol (PS) wurde mit gepfropftem thermomechanischem Zitterpappel- und Birkenzellstoff verstärkt bzw. gefüllt. Die Abhängigkeit der Zugfestigkeitseigenschaften der Verbundstoffe von verschiedenen Gehalten an Füllstoff, vom Polymergehalt der gepfropften Faser, von der Anwesenheit von Homopolymerem in der gepfropften Faser und von der Imprägnierung der Fasern mit PS wurde untersucht. PS, das mit gepfropftem Zitterpappel- und Birkenzellstoff gefüllt war, zeigte eine deutliche Verbesserung der Zugfestigkeit und des Spannungswertes. Die Bruchenergie und die Dehnung der Verbundstoffe nahm mit Zunahme der Konzentration an Füllstoff ab.
    Notes: Polystyrene (PS) was reinforced/filled with grafted thermomechanical pulp (TMP) of aspen and birch. The dependence of tensile properties of composites on different loadings of filler, on polymer loading in grafted fiber, on the presence of homopolymer in grafted fiber, and on impregnation of fibers with PS were studied. PS filled with grafted aspen and birch (lower polymer loading) showed a significant increase in tensile strength and modulus. Fracture energy and elongation of the composites decreased with an increase in the concentration of filler.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051730108
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 121
    Electronic Resource
    Electronic Resource
    Radical concentration and efficiency of secondary photochemical reactions in modified polystyrene (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 165 (1989), S. 153-164 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde der Einfluß der durch Terpolymere modifizierten Polystyrolfilme auf ihre Widerstandsfähigkeit gegenüber UV-Strahlung untersucht.ESR, IR, UV, Massenspektroskopie sowie Viskositäts- und Löslichkeitsmessungen ergeben, daß 3% ABS oder MBS in den Polystyrolfilmen einen bedeutenden Einfluß auf die photochemischen Prozesse hat. Proben mit Terpolymeren, die mit UV-Licht bestrahlt waren, weisen auf eine größere Konzentration von Radikalen mit kürzerer Halbwertszeit hin. Beide Terpolymere bewirken eine höhere Ausbeute der Photooxidation und Vernetzung des Polystyrols und setzen seine Photodehydrierung herab.
    Notes: The influence of acrylonitrile-butadiene-styrene-terpolymer (ABS) and methyl methacrylate-butadiene-styrene-terpolymer (MBS) modifying the polystyrene (PS) films on its resistance to UV radiation were investigated.On the basis of the results of ESR, IR, UV, mass spectroscopy, viscosimetric and solubility measurements it was found that 3% of ABS or MBS in polystyrene films have a clear influence on the course of photochemical processes. After UV-irradiation of the samples, at the presence of this terpolymers, a greater concentration of free radicals with shorter half-life times was observed.Both terpolymers increase the productivity of photooxydation of polystyrene as well as its crosslinking and decrease its dehydrogenation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051650113
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 122
    Electronic Resource
    Electronic Resource
    Synthese und Charakterisierung von Epoxidharzen aus Bisphenol A, Cyanursäuure und Epichlorhydrin (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 173 (1989), S. 219-243 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Epoxy resins of Bisphenol A, cyanuric acid, and their mixtures were synthetized with epichlorohydrin. The obtained products were characterized by gel permeation chromatography, FT-IR-spectroscopy, 1H-NMR-, 13C-NMR-spectroscopy and DSC-analysis. During the syntheses besides the glycidyl-derivatives of Bisphenol A and cyanuric acid also biuret-derivatives were formed as a result of cracking the isocyanurate-ring. The formed resins of Bisphenol A-cyanuric acid mixtures can be crosslinked by heat without additional curing agents.
    Notes: Aus Bisphenol A, Cyanursäure und deren Mischungen wurden mit Epichlorhydrin Epoxidharze hergestellt. Die entstandenen Produkte wurden durch Gelpermeationschromatographie, FT-IR-, 1H-NMR-, 13C-NMR-Spektroskopie und DSC-Analyse charakterisiert. Bei den Synthesen entstehen außer den Glycidylderivaten von Bisphenol A und Cyanursäure Spaltprodukte des Isocyanuratringes bzw. deren Glycidylderivate. Die erzeugten Mischharze lassen sich ohne Härtungsmittel in der Wärme vernetzen.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051730118
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 123
    Electronic Resource
    Electronic Resource
    Lyotropic liquid crystalline polymersPaper presented at the meeting of the GDCH-Fachgruppe “Makromolekulare Chemie” on “Polymers and Biological Functions” in Bad Nauheim (West Germany) on April 18/19, 1988 (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 166 (1989), S. 109-110 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051660107
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 124
    Electronic Resource
    Electronic Resource
    Interaction of amphiphilic polymers with model membranes (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 166 (1989), S. 71-80 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The lipid bilayers of cell membranes are usually connected to two types of biopolymers: the cytoskeleton and the glycocalix. These structures are not only responsible for the stabilization of the lipid bilayer, they also alter the surface properties of the cells. Among the various attempts to mimick membrane properties using polymeric systems(1), one method is the fixation of amphiphilic polymers via hydrophobic anchor groups to lipid bilayers. In the experiments reported here the influence of amphiphilic polymers on the morphology of giant unilamellar liposomes has been investigated. Therefore a series of amphiphilic polyvinylpyrrolidone and dextran derivatives has been synthesized. The fixation of these polymers to the liposomal membranes could be shown with a fluorescence-labelled derivative by using epifluorescence microscopy. The polymer-membrane interaction caused by the insertion of the anchor groups leads to drastic morphological changes in this model membrane system. The exclusive interaction with the outer membrane of multilamellar liposomes could be demonstrated by freeze fracture electron microscopy. In addition, the anchoring of a natural capsular polysaccharide in liposomes has been proven by immunofluorescence. In these experiments, also a clustering (patching) of the antigen caused by the binding of the antibody could be observed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051660105
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 125
    Electronic Resource
    Electronic Resource
    Thermal and dyeing properties of acrylonitrile-glycidyl methacrylate copolymers (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 91-108 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Copolymerisation von Acrylnitril (AN) und Glycidylmethacrylat (GMA) in Tetrahydrofuran wurde untersucht. Die Reaktivitältsverhältnisse wurden bestimmt und das thermische Verhalten der Homo- und der Copolymeren wurde mit Hilfe der Differentialthermoanalyse (DTA) und der Thermogravimetrie (TG) untersucht. Es wurde gefunden, daß GMA beim Aufheizen die Nitriloligomerisationsreaktion initiiert. Die Anfärbbarkeit und die Bleichung in UV-Licht wurden ebenfalls untersucht. Verglichen mit Homopolyacrylnitril zeigen die Copolymeren bessere Affinität gegen basische Farbstoffe. Diese Affinität steigt mit zunehmendem GMA-Anteil im Copolymeren an.
    Notes: The copolymerization of acrylonitrile (AN) with glycidyl methacrylate (GMA) has been investigated in tetrahydrofuran (THF). The reactivity ratios were estimated and the thermal behaviour of the homo- as well as the copolymers, both in air, and under nitrogen atmosphere was investigated using differential thermal analysis (DTA) and thermogravimetry (TG) techniques. GMA was found to initiate the nitrile oligomerization reaction in the copolymers upon heating. The dyeing ability, as well as the colour fastness towards UV light have also been investigated. It was found that the copolymers showed better affinity towards basic dyes compared to homopolyacrylonitrile. This affinity increases with increasing the GMA content in the copolymer.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680107
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 126
    Electronic Resource
    Electronic Resource
    DSC studies on melt crystallized, drawn and fuming nitric acid oxidized polyethylene (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 109-117 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Unverstreckte und verstreckte Polyethylene mit unterschiedlichen Molekulargewichten wurden mit Salpetersäure oxidiert. Der Einfluß der Oxidation auf die Schmelz- und Kristallisationstemperatur der Polymeren wurde mittels Differentialkalorimetrie untersucht.
    Notes: Melting, recrystallisation and remelting of undrawn and drawn linear polyethylene with different molecular weight were studied by differential scanning calorimetry before and after oxidation with nitric acid.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680108
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 127
    Electronic Resource
    Electronic Resource
    Thermal stability of polyurethanes with carbon-carbon crosslinks (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 119-127 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die thermischen Eigenschaften von nur durch C—C-Bindungen vernetzten Polyurethanen aus 4,4′-Diphenylmethandiisocyanat und Poly(ethylenadipat) wurden mit Hilfe der isothermen und nicht-isothermen Thermoanalyse in Stickstoffatmosphäre untersucht. Die thermische Stabilität von diesen Polyurethanen wurde mit der Stabilität von früher untersuchten, mit Allophanat-Bindungen vernetzten Polyurethanen verglichen.Es wurde festgestellt, daß die chemische Struktur der Vernetzungsbindungen das Anfangsstadium des Abbauprozesses bestimmt.
    Notes: Thermal properties of polyurethanes based on 4,4′-diphenylmethane diisocyanate and poly(ethylene adipate) crosslinked only by C—C linkages were studied by isothermal and non-isothermal thermogravimetry carried out in nitrogen atmosphere. Previously studied polyurethanes crosslinked only with allophanate groups were used for comparison.It was found that the structure of crosslinks determines the initial stage of degradation process.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680109
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 128
    Electronic Resource
    Electronic Resource
    Chemical dehydrofluorination and electrical conductivity of poly(vinylidene fluoride) films (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 205-216 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die Dehydrofluorierung von Polyvinylidenfluorid (PVDF)-Pulvern und -Filmen durch verschiedene basische Lösungen untersucht. Speziell die Reaktivität von 1,8-Diazabicyclo[5.4.0]-7-undecen (DBU) in Ethanol, KOH in 2-Propanol und wäßriger NaOH-Lösung mit Tetrabutylammoniumbromid wurde mit Hilfe von Veränderungen der Absorptionsbanden von PVDF-Filmen im Infrarot-(IR) und Ultraviolett-sichtbaren Bereich (UV-VI) untersucht. Neben den durch DBU oder KOH bewirkten Eliminierungsreaktionen treten sicherlich auch Substitutionsreaktionen auf. Die elektrische Leitfähigkeit von dehydrofluorierten PVDF-Filmen nimmt durch Dotierung mit Iod merklich zu, und die Aktivierungsenergien der Leitung liegen zwischen 0,4 und 0,5 eV. Verstrecken eines dehydrofluorierten und mit Iod dotierten PVDF-Films führt zu einer Anisotropie der Leitfähigkeit.
    Notes: The dehydrofluorination of poly(vinylidene fluoride) (PVDF) powder and films was studied using several kinds of base solution. Especially the reactivity of 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) in ethanol, KOH in 2-propanol and aqueous NaOH solution with tetrabutylammonium bromide was investigated by the change in infrared (IR) and ultraviolet-visible (UV-VI) absorptions of PVDF films. The elimination reactions by DBU or KOH were considered to be accompanied by substitution reaction. The electrical conductivity of dehydrofluorinated PVDF films increased markedly by doping with iodine, and the activation energies of conduction were found to be between 0.4 and 0.5 eV. When a drawn PVDF film was dehydrofluorinated and doped with iodine, anisotropy in conductivity was observed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680117
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 129
    Electronic Resource
    Electronic Resource
    Nylon 6/poly(ethylene terephthalate) polymer blends: Rheological properties of melts (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 29-36 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Schmelzrheologische Untersuchungen an Nylon 6/Polyethylenterephthalat (PETP) Blends (PETP-Gehalt zwischen 10 und 50%) wurden mit Hilfe eines Kapillar-Rheometers mit Schergeschwindigkeiten im Bereich von 58 s-1 bis 1,15 · 103 s-1 durchgeführt. Mit steigendem PETP-Gehalt im Blend wurde eine Abnahme der Schmelzviskosität und des nicht-Newtonschen Verhaltens beobachtet. Die Modellgleichung, von Uemura und Takayanagi für viskoelastisch schmelzende Blends entwickelt, wurde zum besseren Verständnis der Dispersion und Morphologie der Nylon 6/PETP-Blends benutzt. Ferner wurde eine umgekehrt proportionale Beziehung zwischen der Schmelzviskosität (η) und dem Elastizitätsmodul (E') von Fasern beobachtet.
    Notes: Melt rheological studies of nylon 6/polyethylene terephthalate (PETP) blends (PETP content varying from 10 to 50%) were carried out using capillary rheometer in the shear rate range of 58 s-1 to 1.15 · 103 s-1. With increasing PETP content in the blend a decrease of the melt viscosity as well as non-Newtonian behaviour was observed. The model equation developed by Uemura and Takayanagi for viscoelastic melt blends has been used to understand the state of dispersion and morphology of a nylon 6/PETP blend system. Further, an inverse relationship between polymer melt viscosity (η) and elastic modulus (E') of fibres was observed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690103
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 130
    Electronic Resource
    Electronic Resource
    Antioxidants and stabilizers, 109Part 108 cf. Stabinform 12 (1987) 17.. The reaction between antioxidant N,N′-diphenyl 1,4-phenylene diamine and 1-cyano-1-methylethyl (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 37-48 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Wirkungsmechanismus des Antioxidans N,N′-Diphenyl-1,4-phenylendiamin (I, DPPD) wurde bei Modellbedingungen untersucht. Die Verbindung I reagiert nach der Oxidation zum Semichinonradikal VIII oder Wursters Kation IX mit 1-Cyano-1-methylethyl (Modellradikal) auf zwei verschiedenen Wegen, und die Reaktion wird durch schwache Säuren beschleunigt. Eine Reaktionsweise führt zur Bindung von Alkyl an Stickstoff unter Bildung von Verbindung III. Diese Verbindung ist unbeständig und, besonders in Gegenwart von Säuren, spaltet leicht Olefin unter Regeneration von DPPD ab. Dieses Verhalten ist ein Modell des Regenerationsmechanismus beim Stabilisierungseffekt von DPPD. Bei diesem Mechanismus werden Alkylperoxy- und Alkylradikale, wührend der Alterung der Kohlenwasserstoffsubstrate unter der Bedingung von relativem Sauerstoffmangel durch DPPD und seinem Oxidationsprodukt (VIII oder IX) desaktiviert. Der zweite Weg führt zur Bindung von Alkyl an den Benzolring unter Bildung von den Verbindungen IV und V. Er stellt so ein Modell für die Bindung von DPPD in die Polymerkette oder auch bei der Vernetzung der Polymerkette während der Alterung des mit DPPD stabilisierten Polymeren dar. Die Verbindung IV unterliegt wegen der Anwesenheit einer Nitrilgruppe noch anderen Veränderungen, bei denen die Verbindungen VI und VII entstehen.
    Notes: The mechanism of action of an antioxidant, N,N′-diphenyl-1,4-phenylene diamine (I, DPPD)Decoding of abbreviations see p. 48., was investigated under model conditions. After oxidation to a semiquinone radical, phenyl (4-phenylamino phenyl)aminyl (VIII), or to Wurster's cation phenyl (4-phenylamino phenyl)ammoniumyl (IX), I reacts with 1-cyano-1-methylethyl (model alkyl) by two routes, both of which are accelerated by weak acids. One of these routes results in alkyl being bound to nitrogen with formation of N,N′-diphenyl N-(1-cyano-1-methylethyl)1,4-phenylene diamine (III). The latter compound is labile, and particularly in the presence of acids readily splits off olefin with regeneration of DPPD. This behaviour is a model of the regeneration mechanism of the stabilizing effect of DPPD, which alternately with its oxidation product (VIII or IX) deactivates the alkylperoxyl and alkyl radicals during the ageing of hydrocarbon substrates under conditions of the relative deficiency of oxygen. The other route leads to binding of the alkyl in the benzene ring with formation of N,N′-diphenyl 2-(1-cyano-1-methylethyl) 1,4-phenylene diamine (IV) and N,N′-diphenyl 2-(1-cyano-1-methylethyl) 1,4-benzoquinone diimine (V), thus modelling the binding of DPPD in the polymer chain, and even the crosslinking of the chain during the ageing of a polymer inhibited with DPPD. Due to the presence of the nitrile group, IV undergoes some further changes, which give rise to the formation of 3,3-dimethyl 2-imino-1-phenyl 5-phenylamino indoline (VI) and 2-acetylimino 3,3-dimethyl-1-phenyl 5-phenylamino indoline (VII).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690104
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 131
    Electronic Resource
    Electronic Resource
    Sphärische ionotrope gele carboxygruppenhaltiger cellulosederivate als trägermaterialien für biologische wirkstoffe, I. Struktur- und quellungsuntersuchungen an xerogelen aus carboxymethylcellulose und aluminiumionen (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 69-82 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Insoluble spherical xerogel particles of aluminium carboxymethyl cellulose are prepared by partial drying of ionotropic gels formed by dropping aqueous solutions of sodium carboxymethyl cellulose into crosslinking solutions of aluminium salts. The swelling ability of the porous and mechanically stable carriers, which are surrounded by a dense surface, rises by partial transformation of carboxy groups into the sodium salts and diminishes with growing content of free acid groups and increasing temperature of drying.
    Notes: Unlösliche sphärische Aluminiumcarboxymethylcellulose-Xerogelpartikel werden durch partielle Trocknung ionotroper Gele hergestellt, die durch Eintropfen wäßriger Lösungen von Natriumcarboxymethylcellulose in vernetzende Aluminiumsalzlösungen entstehen. Das Quellvermögen der porösen und mechanisch stabilen Trägermaterialien, die von einer dichten Außenschicht umgeben sind, erhöht sich durch partielle Umwandlung von Carboxygruppen in die Natriumsalze; es verringert sich mit zunehmendem Gehalt an freien Säuregruppen und steigender Trocknungstemperatur.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690107
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 132
    Electronic Resource
    Electronic Resource
    Modification of polybutadienes by catalytic and photochemical decomposition of dimethyldiazomalonate (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 93-100 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Modifizierung von Polybutadien durch katalytische und photolytische Spaltung von Dimethyldiazomalonat (dmdm) wird beschrieben. Durch diese Methode werden hochreaktive Carbene erzeugt, die die Bildung von Additions- und Insertionsprodukten bewirken. Die chemischen Strukturen der modifizierten Polymeren wurden durch NMR-Spektroskopie bestätigt. Auch Carbendimere wurden in nicht unbedeutendem Maße gebildet, was vom Molekulargewicht und der Mikrostruktur des Ausgangspolymeren abhängt.
    Notes: Modifications of polybutadienes via catalytic and photolytic decomposition of dimethyldiazomalonate (dmdm) are described. This method pertains to the generation of highly reactive carbenes which give rise to the formation of addition and insertion products. Chemical structures of the modified polymers were confirmed by NMR spectroscopy. It was found that carbene dimers were also formed in a significant extent depending on the molecular weight and microstructure of the initial polymers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690109
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 133
    Electronic Resource
    Electronic Resource
    Grafting of N-methylolacrylamide onto flax/polyester fabric using ferrous cellulose thiocarbonate/H2O2 redox system (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 101-117 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die pfropfcopolymerisation von N-Methylolacrylamid auf Flachs/Polyester-Mischgewebe mit Hilfe eines Eisen/Cellulosethiocarbonat/H2O2-Redoxsystems wurde unter verschiedenen Bedingungen, wie Wasserstoffperoxid-Konzentration (1-60 mmol/l), Eisen-Ammoniumsulfat-Konzentration (1-50 mmol/l), N-Methylolacrylamid-Konzentration (5-200%, bezogen auf das Probengewicht), Polymerisationszeit (10-90 min), Temperatur (20-50°C) und pH-Wert des Mediums (1,1-11) untersucht. Zur Berechnung der Pfropfausbeute wurde der Stickstoff-und/oder der Methylolgehalt benutzt. Die erhaltenen Ergebnisse zeigen, daß die Pfropfausbeute, die durch Stickstoffanalyse bestimmt wurde, umso h6her ist, je mehr die H2O2-Konzentration steigt; ab 40 mmol/l bleibt die Ausbeute konstant. Auf der anderen Seite hat die Pfropfausbeute, die aus dem Methylolgehalt bestimmt wurde, einen Maximalwert bei 10 mmol/l H2O2. Die Ergebnisse zeigen, daß die Pfropfung sehr begünstigt abliruft, wenn die Reaktion mit 1 mmol/l Eisen-Ammoniumsulfat bei einem pH von 4,4, einer Temperatur von 30°C und 60 min lang durchgefuhrt wird. Die Aktivierungsenergie der Copolymerisationsreaktion betrirgt 9,74 kJ/mol, und die Pfropfausbeute steigt mit steigender N-Methylolacrylamid-Konzentration. Weiterhin wurde ein Vergleich der Polymerisatonswirksamkeit in Bezug auf die Pfropfung von N-Methylolacrylamid auf Flachs/Polyester-Mischgewebe zwischen einem Eisen-/Cellulosethiocarbonat/H2O2- und einem Eisen/H2O2-Redoxsystem durchgefuhrt. Diese beiden Systeme wurden bezuglich der Pfropfausbeute, des Homopolymeranteils, des Gesamtumsatzes, des Pfropfungsgrades und des Polymerisationsgrades des Homopolymeren untersucht.
    Notes: Graft copolymerization of N-methylolacrylamide onto flax/polyester blend fabric using ferrous cellulose thiocarbonate/H2O2 redox system was investigated under different conditions including hydrogen peroxide concentration (1-60 mmol/l), ferrous ammonium sulphate concentration (1-50 mmol/l), N-methylolacrylamide concentration (5-200%, based on weight of sample), polymerization time (10-90 min), temperature (20-50°C), and pH of the medium (1.1-11). The nitrogen content and/or the methylol content were used for calculation of graft yields. Results obtained indicated that graft yields, derived from nitrogen analysis, are higher the greater the H2O2 concentration increases till 40 mmol/l, then level off. On the other hand, graft yields derived from methylol content exhibit maximum value at 10 mmol/l H2O2. The results indicate also that grafting was highly favoured when it was carried out using 1 mmol/l ferrous ammonium sulphate and pH 4.4 at 30°C for 60 min. The apparent activation energy of the copolymerization reaction amounts to 9.74 kJ/mol. Furthermore, the graft yield increases by increasing N-methylolacrylamide concentration within the range studied. The work was further extended to include a comparison between the polymerization efficiencies of the ferrous cellulose thiocarbonate/H2O2 redox system and the ferrous/H2O2 redox system in inducing grafting of N-methylolacrylamide onto flax/polyester blend fabric. For this reason, the two systems were studied with respect to graft yield, homopolymer proportion, total conversion, graft efficiency, and homopolymer efficiency.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 134
    Electronic Resource
    Electronic Resource
    Structural studies on chars from fire retardant intumescent systems (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 137-142 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Flammschutz von Polymeren durch Entstehung von intumeszierender Kohle wird allgemein auf die physikalischen isolierenden Eigenschaften der bei der Verkohlung entstehenden Oberfläche zurückgeführt. Diese Eigenschaften wiederum hängen von der physikalisch-chemischen Struktur der Kohle ab, über die nur wenig bekannt ist. Es wird gezeigt, daß die Elektronenrastermikroskopie und Mikroanalyse durch ein energiedispersives System Aufschluß geben über die Morphologie und Zusammensetzung solcher intumeszierender Systeme. Die erhaltenen Daten tragen zum Verständnis der Schwerentflammbarkeit bei.
    Notes: The protection provided by intumescent chars against the action of the flame is generally attributed to their physical insulating properties. These in turn depend on the physical chemical structure of swollen char, which however has been scarcely studied. It is shown that scanning electron microscopy and microanalysis by energy dispersive system supply detailed information on the morphology and the chemical composition of intumescent systems. The data obtained contribute to the understanding of the fire retardance mechanism.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690112
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 135
    Electronic Resource
    Electronic Resource
    A study of CO2 and excimer laser treatments of poly(etheretherketone) (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 169 (1989), S. 143-151 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: CO2- und Eximer-Laser-(193, 248, 350 nm) Behandlungen wurden an Polyetheretherketon (PEEK) vorgenommen. Hochintensive Eximer-Laser-Strahlung verursacht wirksame Ätzung, hauptsächlich durch thermische Effekte. Die Bestrahlung mit CO2-Lasern und hochintensiven Eximer-Lasern führt zu Änderungen in der Oberflächenchemie und -morphologie.Intensitätsschwache Eximer-Laser-Bestrahlung bei 193 und 248 nm begünstigt das Auftreten photochemischer Phänomene. Die chemische Modifizierung der Oberfläche führt zur Sauerstoffabnahme, und eine bevorzugte Eliminierung der Ketonbrücke wurde festgestellt. Gleichzeitig wurden morphologische Veränderungen der Oberfläche gefunden; Beugungseffekte führen zu konischen Strukturen, und die Abscheidung größerer Oligomerer bewirkt die Bildung von Ablagerungen auf der Oberfläche.
    Notes: CO2 and excimer laser (193, 248, 350 nm) treatments were performed on poly(etheretherketone) (PEEK). High fluence excimer laser irradiation induced efficient etching, mainly due to thermal effects. The irradiation with CO2 lasers and high fluence excimer lasers introduced limited changes in surface chemistry and morphology.Low fluence excimer laser irradiation, particularly at 193 nm and 248 nm, favored the occurence of photochemical phenomena. Surface chemical modifications leading to oxygen depletion and preferential elimination of the ketonic bridge were assessed. At the same time surface morphological alterations were found, diffraction effects led to cone-like structures while the redeposition of heavy oligomers caused the formation of debris on the surface.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051690113
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 136
    Electronic Resource
    Electronic Resource
    Morphology and supermolecular structure of the polymer system PA-6/PMA (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 9-21 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Ergebnisse von Untersuchungen über die molekulare Überstruktur von Mischungen aus teilkristallinem Polyamid-6 (PA-6) und amorpher Poly(methacrylsäure) (PMA) werden vorgestellt.Die Bestimmung der molekularen Überstruktur gelang durch Berechnung von Korrelationsfunktionen und Grenzflächenverteilungsfunktionen aus SAXS-Aufnahmen.Der Einbau von Poly(methacrylsäure) bewirkt eine Transformation der Kristallstruktur des PA-6 vom γ-Typ zum α-Typ. Bei einem PMA-Gehalt von weniger als 46% hat die Mischung eine lamellare Struktur; ein zunehmender PMA-Anteil vergrößert die Langperiode. PMA bildet mit dem amorphen Anteil von PA-6 eine homogene Phase; Mikrodomänen werden nicht beobachtet.Mit zunehmendem PMA-Gehalt sinkt der Kristallinitätsindex. Gleichzeitig nimmt die Dicke der Übergangsschicht zwischen den kristallinen Regionen und der aus PMA und amorphem PA-6 bestehenden Phase zu. Bei hohem PMA-Gehalt verschwindet die lamellare Struktur.
    Notes: The results of investigations of the supermolecular structure of the mixture of a semicrystalline polymer polyamide-6 (PA-6) and of an amorphous one, poly(methacrylic acid) (PMA), are presented. The determination of the supermolecular structure was realized using the correlation functions and the interface distribution functions calculated from SAXS patterns. It was stated that the introduction of poly(methacrylic acid) results in a transformation of the γ-type crystalline structure into the α-type structure. Until the PMA content is less than 46%, the blend has a lamellar structure, and an increase in the PMA content causes an increase in the long period. PMA and the amorphous phase of PA-6 form a homogeneous phase, there are no microdomains of PMA.An increase in the PMA content results in a decrease of the crystallinity index. Simultaneously, the thickness of the transition layers between the crystalline regions and the phase composed of PMA and of the amorphous phase of PA-6 increases. When the content of PMA is large, the lamellar structure disappears.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680102
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 137
    Electronic Resource
    Electronic Resource
    N-substituted maleimides as thermal stabilizers for rigid polyvinylchloride (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 23-35 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: N-substituierte Maleinimide sind thermische Stabilisatoren für Hart-Polyvinylchlorid (PVC). Dies wurde durch Messung der Dehydrochlorierungsrate und des Ausmaßes der Verfärbung des Polymeren bei 180°C in Luft untersucht. Die Ergebnisse zeigen die höhere Stabilisierungswirkung dieser Produkte im Vergleich zu Stabilisatoren wie basisches Bleicarbonat, Dibutylzinnmaleat und Cadmium-Bariumstearat, die üblicherweise in der Industrie benutzt werden. Die Induktionszeit (Ts) steigt in dem Maße, in dem der positive Resonanzeffekt (+R) der Substituenten zunimmt. Ferner bewirken die untersuchten Stabilisatoren gegenüber Stearatstabilisatoren bessere Farbbeständigkeit der abgebauten Proben. Diese Stabilisatoreffektivität ist darauf zurückzuführen, daß der Stabilisator Radikale einfangen kann, die bei dem radikalischen Abbau von PVC entstehen. Die gute Farbstabilität resultiert aus der Fähigkeit des Stabilisators, mit den konjugierten Doppelbindungen, die durch den Abbau des PVC in der Polymerkette entstehen, in Wechselwirkung zu treten. Ein Mechanismus für die Wirkungsweise des Stabilisators wird vorgeschlagen.
    Notes: N-substituted maleimides have been investigated as thermal stabilizers for rigid polyvinylchloride (PVC) at 180°C in air by measuring the rate of dehydrochlorination and the extent of discoloration of the polymer. The results reveal the higher stabilizing efficiency of these products relative to basic lead carbonate, dibutyl tin maleate, and cadmium-barium stearate stabilizers commonly used in industry. The induction period (Ts) increases as a function of the positive resonance effect of the substituents (+R). Moreover, the investigated stabilizers impart better color stability for the degraded samples as compared with the stearate stabilizer. The stabilizer efficiencies are attributed to their radical trapping potency which intervenes with the radical degradation process of PVC, while the good color stability is due to the ability of the stabilizer to interact with the conjugated double bonds formed on the PVC chains as a result of degradation. A mechanism illustrating the stabilizer's action is proposed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680103
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 138
    Electronic Resource
    Electronic Resource
    Mechanische Eigenschaften von Polyesterfasern bei kurzzeitiger Zugbeanspruchung, 1. Aufbau eines Meßplatzes für schnelle Zugbeanspruchung (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 37-52 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The stress-strain behaviour of filament yarns has been determined by variation of strain rates from 10-1 up to 105%/s. Strain rates up to 10%/s are obtained with a tensile testing machine. The higher strain rates up to 105%/s are obtained with an apparatus using a falling weight by variation of the height of fall and the length of the yarn.Because of the high-speed impact and time of strain/influence down to 10-4 s together with the variation of the height of fall between 0,6 and 166 cm a profound discussion of errors is necessary.
    Notes: Kraft-Dehnungs-Graphen von Filamentgarnen für die Dehngeschwindigkeiten zwischen 10-1 und 105%/s werden ermittelt. Für die niedrigen Dehngeschwindigkeiten bis 10%/s wird eine übliche Zugprüfmaschine benutzt, die höheren Dehngeschwindigkeiten werden mit einer Fallschlagapparatur durch Variation der Fallhöhe und der Fadenlänge erreicht.Aufgrund der hohen Dehngeschwindigkeit und der Meßzeiten bis minimal 10-4 s sowie der Variation der Fallhöhe zwischen 0,6 und 166 cm treten Fehler auf, die eingehend diskutiert werden.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680104
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 139
    Electronic Resource
    Electronic Resource
    Reaction of diimide compounds with diglycidyl ether of 4,4′-dihydroxybiphenyl (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 81-89 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Neue Esterimid- und Ketoimidpolymere, die Biphenylgruppen enthalten, wurden synthetisiert und die Strukturen durch thermogravimetrische (TGA) Messungen untersucht. Es zeigte sich eine unterschiedliche Beständigkeit in bezug auf die Struktur des Imides. Die entsprechenden Amid-Imid-Verbindungen wurden als Monomere geprüft, aber die Polymerisation verlief nicht wie erwartet, und es konnten Nebenreaktionen durch 13C-NMR Spektroskopie beobachtet werden.
    Notes: New esterimide and ketoimide polymers containing a biphenyl group have been synthesized and characterized by spectral techniques. Their thermal properties have been studied by thermogravimetric (TGA) measurements, showing a different stability with regard to the imide structure. The analogous amide imide compounds have been tested as monomers, but their polymerization has not taken place as we expected and side reactions have been detected by 13C-NMR spectroscopy.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680106
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 140
    Electronic Resource
    Electronic Resource
    Mechanische Eigenschaften von Polyesterfasern bei kurzzeitiger Zugbeanspruchung, 2Teil 1: cf. Lit.5. Verformungsgeschwindigkeitsabhängige Kraft-Dehnungs-Diagramme von Polyester-Multifilamentgarn (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 168 (1989), S. 53-79 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polyethylene terephthalate (PETP) multifilament yarns with different thermal history were used as testing materials.The stress-strain curves for strain rates from 0.1 up to 100 000%/s show that the maximum tensile force increases and the elongation decreases with increasing strain rate. However, there are differences for yarns with different thermal history. So a free of stress treated yarn shows less change of the maximum tensile force with increasing strain rate than a yarn treated at the same temperature but under stress. The elongation by the maximum tensile force shows the opposite behaviour. With increasing influence of the elongation rate to the force of rupture the ratio of the maximum tensile force and the relevant elongation increases faster.The initial slope (modulus) of the stress-strain curves of the multifilament yarn increases for all futed stresses and temperatures with the strain rate. The local minimum of the modulus curves shifts to higher modulus with increasing strain rate while the position of the minimum as a function of the elongation remains constant.
    Notes: Untersucht werden Polyethylenterephthalat (PETP)-Multifilamentgarne mit unterschiedlicher thermischer Vorgeschichte.Die Kraft-Dehnungs-Kurven für die Dehngeschwindigkeit von 0,1 bis 100 000%/s zeigen, daß die Höchstzugkraft mit der Dehngeschwindigkeit zunimmt und die Höchstzugkraftdehnung abnimmt. Für die Garne mit unterschiedlicher thermischer Vorgeschichte bestehen jedoch Unterschiede, was die Änderung der Höchstzugkraftund Höchstzugkraftdehnungswerte mit der Dehngeschwindigkeit betrifft. So weist ein spannungslos thermisch behandeltes Material eine geringere Änderung der Höchstzugkraft mit steigender Dehngeschwindigkeit auf als ein bei gleicher Temperatur, aber unter Spannung thermofixiertes Material. Die Höchstzugkraftdehnungswerte zeigen dagegen ein umgekehrtes Verhalten. Mit wachsendem Einfluß der Dehngeschwindigkeit auf die Bruchkraft nimmt das Verhältnis von Höchstzugkraft zu Höchstzugkraftdehnung stärker zu.Die Anfangssteigung, d. h. der Anfangsmodul der K-D-Kurven des Fadenmaterials, nimmt für alle Fixierspannungen und -temperaturen mit der Dehngeschwindigkeit zu. Das lokale Minimum der ersten Ableitung der K-D-Kurven (lokales Modulminimum) verlagert sich mit zunehmender Dehngeschwindigkeit zu höheren Modulwerten, die Lage des Minimums als Funktion der Dehnung bleibt jedoch konstant.
    Additional Material: 27 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051680105
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 141
    Electronic Resource
    Electronic Resource
    Preparation and characterization of dimethylacrylamide based polymer supports (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 43-57 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird über eine systematische Studie über die Herstellung von Dimethylacrylamid-Harzen, die Amino- oder Carboxylgruppen tragen, berichtet. Details werden über die Synthesen von Dimethylacrylamid (1) und einer Zahl vernetzender (2) und funktionelle Gruppen tragender (3-5) Monomerer auf Acrylamid-Basis mitgeteilt. Es wird die Terpolymerisation von 1 und 2 mit 3 (oder mit 4 oder 5) in Wasser/Öl-Suspension beschrieben, die zu Harzen mit weitem Bereich von Funktionalität und Quellverhalten führt. Die Quellfähigkeit verschiedener Harzproben in Dichlormethan, Dimethylformamid, Dimethylsulfsoxid, Methanol, Essigsäure und Wasser wurde festgestellt. Ferner werden typische chemische Umsetzungen von Dimethylacrylamid-Harzen beschrieben.
    Notes: A systematic study of the preparation of dimethylacrylamide resins carrying amino, carboxyl or activated carboxyl functionality is reported. Details of the syntheses of dimethylacrylamide (1) and a number of acrylamide-based crosslinking (2) and functional (3-5) monomers are given. The terpolymerization of 1 and 2 with 3 (or with 4 or 5) by a water in oil (w/o or reverse) suspension polymerization procedure is described for the preparation of dimethylacrylamide resins having a wide range of functionality and swelling behaviour. The swellability of several of the resin samples in dichloromethane, dimethylformamide, dimethylsulfoxide, methanol, acetic acid, and water is given. Typical chemical transformations of dimethylacrylamide resins are also described.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051700103
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 142
    Electronic Resource
    Electronic Resource
    Synthesis and some properties of carbazole modified polyvinylchloride and the cation exchange resin therefrom (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 115-125 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Substitution von Chlor in PVC durch 3,6-Diamino-N-methyl-carbazol entsteht ein Kondensat, das in allen Lösungsmitteln für PVC unlöslich ist. Dieses Kondensat ist thermisch stabiler als PVC. Auch die dielektrischen Eigenschaften unterscheiden sich deutlich von denen von PVC. Die Sulfonierung des PVC-Carbazol-Kondensats liefert ein Kationenaustauscherharz mit SO3H- und COOH-Gruppen.
    Notes: The chlorine displacement reaction between PVC and N-methylcarbazole-3,6-diamine affords a condensate which is insoluble in all possible solvents of PVC. The overall thermal stability of this condensate is appreciably higher than that of PVC. The dielectric behavior is also significantly different from that of unmodified PVC. Sulfonation of the PVC-carbazole condensate affords a cation-exchange resin with —SO3H and —COOH functional moieties.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051700108
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 143
    Electronic Resource
    Electronic Resource
    Unvernetzte Epoxid-Amin-Additionspolymere, 2120. Mitteilung s. Lit.1.. Dimethyl(aminomethyl)phosphinoxid, ein comonomeres für epoxidpolymere mit verminderter entflammbarkeit (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 145-157 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Synthesis and Oxygen index (OI) of linear epoxide-amine addition polymers and prepolymers containing (dimethylphosphinyl)methanamine (DMAPO) as flame retardant unit were studied.The structural feature of these polymers and prepolymers was determined by elemental analysis, IR-, 1H-NMR-, 13C-NMR- and 31P-NMR spectroscopy.The OI of the addition polymer of bisphenol-A diglycidylether and DMAPO was found to be 29.5.
    Notes: Es wird über die Herstellung von linearen, hochmolekularen Epoxid-Amin-Additionspolymeren und telechelen Prepolymeren berichtet, die mit Dimethyl(aminomethyl)phosphinoxid (DMAPO) ein flammwidriges Kettenglied in der Polymerkette enthalten. Die Struktur dieser Polymeren und Prepolymeren wird mittels Elementaranalyse, Mn-Werten, IR-, 1H-NMR-, 13C-NMR- und 31P-NMR-Spektroskopie untersucht. Der Sauerstoffindex OI von DGEBA/DMAPO-Polymeren erreicht etwa 30.Auch der polare Charakter von Epoxid/Amin-Additionspolymeren, der für die Haftung an metallischen und oxidischen Werkstoffen bedeutsam ist, wird durch den Einbau von PO(CH3)2-Gruppen verstärkt. Ebenso wird hierdurch die photooxidative Stabilität verbessert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051700111
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 144
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of some 2,4′-dibenzyldiisocyanate ionic polymers. V. Ionene polymersPart IV cf. lit.4. (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 183-190 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Kationische Polyurethane mit Piperazinringen in der Polymerkette wurden durch eine Menschutkin-Reaktion dargestellt. Ein Prepolymer mit tertiären Dimethylaminoendgruppen und ein Dihalogenid wurden für die erste Stufe verwendet, N,N′-Dimethylpiperazin für die zweite Stufe. Das viskosimetrische Verhalten der verdünnten Lösungen in Lösungsmitteln mit hohen Dielektrizitätskonstanten wurde untersucht.
    Notes: Cationic polyurethanes containing piperazine rings on the macromolecular chain were synthesized by a Menschutkin reaction. A prepolymer with tertiary dimethylamino end groups and a dihalide were used in the first step, and N,N′-dimethylpiperazine in the second step. The viscometric behaviour of dilute solutions in solvents with high dielectrical constants was studied.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051700114
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 145
    Electronic Resource
    Electronic Resource
    Polyamines containing β-hydroxyurethane linkages as curing agents for epoxy resin (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 170 (1989), S. 211-225 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Synthesemethode für modifizierte Aminhärter mit β-Hydroxyurethanbindungen wird vorgestellt. Die physikalischen und chemischen Eigenschaften der modifizierten Polyamine, wie Viskosität und Reaktivität gegenüber einem Epoxidharz, wurden untersucht. Im Vergleich zu einem unmodifizierten Amin wurde eine Verkürzung der Gel- und Härtungszeit in Verbindung mit einer Verringerung des exothermen Effekts während der Härtung eines Epoxidharzes gefunden. Mechanische und thermomechanische Untersuchungen zeigten einen Anstieg der Erweichungstemperaturen, der Härte und der Festigkeitseigenschaften, wie Zugfestigkeit, Scher- und Schälfestigkeit, bei den mit modifizierten Aminen gehärteten Epoxidharzen im Vergleich zu einem Harz, das mit einem unmodifizierten Amin vernetzt wurde.
    Notes: A method of obtaining modified amine curing agents containing β-hydroxyurethane linkages is presented. The basic physical and chemical properties of the modified polyamines, such as viscosity and reactivity towards epoxy resins, have been studied.A shortening of the gel and curing times in addition to a decrease of the exothermic effect accompanying the curing of an epoxy resin was found in comparison with the system containing an unmodified amine. Mechanical and thermomechanical studies showed a rise of the deflection temperature, hardness and strength features such as tensile strength, shear and peel strength for epoxy resins crosslinked with modified curing agents in comparison with those parameters obtained for resins crosslinked with the initial amines.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051700117
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 146
    Electronic Resource
    Electronic Resource
    Mutual miscibility of chlorinated hydrocarbon polymers derived from polyethylene and polyvinylchlorideDedicated to Prof. Dr. Dr. h. c. H. Hellmann on the occasion of his 75th birthday (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 171 (1989), S. 53-63 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Untersucht wurde die Verträglichkeit von polymeren Chlorkohlenwasserstoffen mit verschiedener Comonomersequenzordnung. Eine erste Copolymerenserie (“PVCx”) wurde durch Reduktion von Polyvinylchorid hergestellt, eine zweite Serie (“PECx”) durch Chlorieren von Polyethylen. Die Polymer-Legierungen PECx/PECy, PVCx/PVCy und PVCx/PECy wurden bei 30°C und 110°C mit einer Lösungsfilmmethode analysiert. Im System PECx/PECy nimmt die Mischbarkeit mit steigendem Chlorgehalt der Copolymeren stetig zu. Bei den Systemen PVCx/PVCy und PVCx/PECy zeigt sich im Bereich um x = 1 eine erhöhte Tendenz zur Phasenseparation, die auf die bessere Comonomersequenzordnung der Copolymeren PVCx zurückzuführen ist. Im letzteren System ist diese Tendenz so stark, daß Polyvinylchlorid (PVCx=1) sogar mit dem chlorierten Polyethylen PECx=1, das die gleiche Bruttozusammensetzung hat, nicht mischbar ist.
    Notes: The compatibility of chlorinated hydrocarbon polymers of two different comonomer sequence orders was investigated. One series of copolymers (“PVCx”) was prepared via reduction of polyvinylchloride, the other (“PECx”) via chlorination of polyethylene in solution. The blends PECx/PECy, PVCx/PVCy and PVCx/PECy were analyzed with a film casting method at 30°C and 110°C. Miscibility increases in the system PECx/PECy steadily in the direction of increasing chlorine content. Due to the comonomer sequence order in the copolymers PVCx the systems PVCx/PVCy and PVCx/PECy show in the range around x = 1 an extra effect favouring phase separation. In the latter system this effect is so strong that polyvinylchloride (PVCx = 1) is even incompatible with the chlorinated polyethylene PECx=1 although both have the same overall composition.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051710104
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 147
    Electronic Resource
    Electronic Resource
    Thermal and viscoelastic behavior of polyetheretherketone/polyethersulfone blends (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 171 (1989), S. 119-130 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die aus Lösung hergestellten Polymermischungen zeigen den Typus der vollmischbaren Polymerlegierungen. Proben, die durch Formpressen der Polymermischungen unterhalb des Schmelzpunkts von Polyetheretherketon (PEEK) erhallten wurden, zeigen ein für mischbare Polymerlegierungen typisches viskoelastisches Verhalten. Hingegen zeigt sich bei Mischungen, die oberhalb des Schmelzpunktes von PEEK verpreßt wurden, im dynamisch-viskoelastischen Verhalten eine Phasentrennung.
    Notes: The polymer blends obtained by the solution blending method show a type of compatible polymer blends. The samples obtained by compression molding the polymer blends below the melting point of the polyetheretherketon (PEEK) exhibit dynamic viscoelastic behavior characteristic of compatible polymer blends, but those by compression molding above the melting point of the PEEK show a phase separation in dynamic viscoelastic behavior.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051710109
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 148
    Electronic Resource
    Electronic Resource
    Study of thermal stimulated current and effect of annealing on cellulose nitrate (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 171 (1989), S. 91-100 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurden Cellulosenitratproben (CN-85) untersucht. Die Leitfähigkeit stieg für ungetemperte Proben mit der Temperatur an und nahm mit zunehmender Temperzeit ab. Die Aktivierungsenergie ist bei allen Proben gleich, sie beträgt 2.1 eV in einem Temperaturbereich von 322 bis 385 K. Das Verhalten ist metallisch (dσ/dT) 〈 0 für Temperzeiten, die mehr als 24 h betragen. Bei den gemessenen thermisch stimulierten Strömen (TSC) verschob sich die Lage des Maximums mit zunehmender Aufheizgeschwindigkeit leicht gegen höhere Temperaturen. Die Aktivierungsenergie im Fall des TSC Stromes betrug 0.21 eV, unabhängig von der Aufheizgeschwindigkeit. Die dipolare Relaxationszeit und scheinbare Dielektrizitätskonstante wurden theoretisch berechnet und als Funktion der Temperatur untersucht.
    Notes: The investigated samples were cellulose nitrate CN-85. The conductivity increases with temperature for unannealed samples and decreases with increasing time of annealing for annealed samples.The activation energy is equal for all samples and amounts to 2.1 eV in a temperature range from 322 to 385 K. The behaviour is metallic (dσ/dT) 〈 0 for times of annealing larger than 24 h. The TSC current was measured. The position of the maximum slightly shifted towards higher temperatures with increasing rate of heating. The activation energy in the case of the TSC current was 0.21 eV and independent of the rate of heating. The dipolar relaxation time and imaginary dielectric constant were calculated theoretically and studied as a function of temperature.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051710107
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 149
    Electronic Resource
    Electronic Resource
    Glutarimide copolymer additive for high service temperature PVC (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 171 (1989), S. 175-190 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde ein Acrylester-Acrylimid-Copolymeres entwickelt, welches als Additiv in Mischungen mit PVC dessen Gebrauchstemperatur erhöht, ohne andere Eigenschaften des PVC, insbesondere die Transparenz, negativ zu beeinflussen.
    Notes: A major disadvantage of PVC is its low glass transition temperature which limits the service temperature of finished articles to about 70°C. An additive has been developed that can be formulated with PVC to form blends with increased service temperature. With proper formulating, higher heat distortion temperatures can be achieved without sacrificing other properties including clarity. This is especially important in clear PVC applications where no increase in haze is noted with the addition of the acrylic/imide copolymer.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051710114
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 150
    Electronic Resource
    Electronic Resource
    Epoxy groups on grafted polypropylene. II. Reaction with amines (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 171 (1989), S. 153-164 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Epoxidgruppen eines Copolymeren, das man durch Pfropfung von 2,3-Epoxypropylmethacrylat auf isotaktisches Polypropylen erhält, wurden mit niedermolekularen sekundären Aminen umgesetzt. Hohe Reaktionsgeschwindigkeiten zeigen heterocyclische Amine. Die Reaktion weniger stark basischer Amine wird in Gegenwart von sauren Katalysatoren beschleunigt. Der Mechanismus des Einflusses des Amin-Säure-Paares auf die Epoxidgruppen auf der Oberfläche eines festen Polymeren unter heterogenen Bedingungen wird diskutiert.
    Notes: Epoxy groups attached to isotactic polypropylene in form of 2,3-epoxypropylmethacrylate grafts were reacted with low molecular secondary amines. Secondary heterocyclic amines exhibit high reaction rates in this process. The bonding of less basic amines is accelerated in the presence of acid catalysts. The mechanism is discussed of amine-acid couple influence upon the epoxy group present in heterogeneous system on the surface of solid polymer.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051710112
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 151
    Electronic Resource
    Electronic Resource
    Ammoniakdiffusion in Polymerfilmen (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 173 (1989), S. 69-84 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: With the help of a novel test method, diffusion-coefficients of ammonia were determined in 22 transparent, filmforming polymers at room temperature. This method is based upon the UV-VIS-spectroscopically followable reversible reaction of ammonia with 4-nitro phenol to a Meisenheimer-complex.The dye-building reaction was studied and analyzed by a simple approximation of the diffusion equation. Diffusion coefficients obtained are in good agreement with the few available data in the literature.The dependence of the NH3-diffusion coefficients upon the polymer structure corresponds with the obtained diffusion coefficients, which are known for permanent gases.The described method allows the measurement of diffusion coefficients, which are distinguished up to three orders of magnitude, without any problem (ethylcellulose: 1,07 · 10-7 cm2 · s-1; poly(vinylalcohol): 0.9 · 10-10 cm2 · s-1).
    Notes: Mit Hilfe einer neuartigen Untersuchungsmethode wurden die Diffusionskoeffizienten von Ammoniak (NH3) in 22 transparenten filmbildenden Polymeren bei Raumtemperatur bestimmt. Die Methode beruht auf der UV-VIS-spektroskopisch verfolgbaren reversiblen Reaktion von Ammoniak mit 4-Nitrophenol zu einem 4-Nitrophenolat-Ammoniak-Meisenheimer-Komplex.Die Farbbildungsreaktion im Polymerfilm wurde untersucht und anhand einer einfachen Näherung der Diffusionsgleichung ausgewertet. Die erhaltenen Diffusionskoeffizienten stimmen sehr gut mit den wenigen verfügbaren Literaturwerten überein.Die Abhängigkeit der NH3-Diffusionskoeffizienten von der Polymerstruktur ist weitgehend der für permanente Gase bekannten analog.Die beschriebene Methode erlaubt problemlos, Diffusionskoeffizienten zu messen, die sich bis zu drei Größenordnungen unterscheiden (Ethylcellulose: 1,07 · 10-7 cm2 · s-1; Polyvinylalkohol: 0,9 · 10-10 cm2 · s-1).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051730106
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 152
    Electronic Resource
    Electronic Resource
    Light scattering studies of bovine skin proteodermatan sulfate (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1295-1308 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proteodermatan sulfate (PDS) of bovine skin is a low molecular weight proteoglycan with a molecular structure consisting of a protein chain and a sulfated polysaccharide chain covalently linked at the 4-serine of the protein. Static and dynamic laser light scattering methods have been used to determine the weight-average molecular weight, Mw, z-average radius of gyration, Rgz′, and z-average translational diffusion coefficient, Dt,z°, of bovine skin PDS. We have also characterized the two components of PDS, i.e., the protein core and the dermatan sulfate (DS) chain. (The latter contained an N-terminal-linked penta- or tetrapeptide.) Interpretation of the PDS data is complicated by the block copolymer nature of its structure. When appropriate corrections are made, our results indicate that Mw for PDS monomer is 62,000 when dissolved in 4M guanidine hydrochloride (GdnHCl), and increases to 610,000 in 0.15M NaCl. Mw for the core protein in 4M GdnHCl is 39,000, and this also increases substantially to 650,000 in 0.15M NaCl. In contrast, Mw for the DS chain is 24,000 in 0.15M NaCl, indicating that there is minimal self-association of DS in 0.15M NaCl. Thus we conclude that the self-association of PDS involves the protein core. Comparison of Rgz and Rh, the average hydrodynamic radius, suggests that trace amounts of aggregation persist for the PDS and its core protein even in 4M GdnHCl. This conclusion is supported by evaluation of the second moments of the dynamic light scattering correlation function. Comparisons of the observed Dt,z° for PDS with predicted values using hydrodynamic theory are consistent with a “lollipop” conformation for the molecule.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280710
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 153
    Electronic Resource
    Electronic Resource
    Solvation thermodynamics of biopolymers. II. Correlations between functional groups (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1327-1337 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extent of correlations between functional groups that can form hydrogen bonds with solvent molecules has been estimated. From the observed distance distribution of functional groups on the surfaces of several proteins, and from the extent of correlation between pairs of such functional grups, we conclude that the assumption of independence of functional groups made in part I is probably a good approximation. The reason is that even when correlations exist there is, on average, cancellation of the positive and negative correlations. The relevance of hydrogen bonding with the solvent to the relative stability of different conformers of biopolymers is also indicated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280712
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 154
    Electronic Resource
    Electronic Resource
    Measurement of electrophoretic mobility of dye-labeled large DNA fragments in agarose gels by movement of fluorescence pattern after photobleaching (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1491-1494 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280813
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 155
    Electronic Resource
    Electronic Resource
    The sieving of spheres during agarose gel electrophoresis: Quantitation and modeling (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1475-1484 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By use of agarose gel electrophoresis, the sieving of spherical particles in agarose gels has been quantitated and modeled for spheres with a radius (R) between 13.3 and 149 mm. For quantitation, the electrophoretic mobility has been determined as a function of agarose percentage (A). Because a previously used model of sieving [D. Rodbard and A. Chrambach (1970) Proc. Natl. Acad. Sci. USA 65, 970-977] was found incompatible with some of these data, alternative models have been tested. By use of an underivatized agarose, two models, both based on the assumption of a single effective pore radius (PE) for each A, were found to yield PE values that were independent of R and that were in agreement with values of PE obtained independently (PE = 118 nm × A-0.74): sieving by altered hydrodynamics in a cylindrical tube of radius, PE, and sieving by steric exclusion from a circular hole of radius, PE. The same analysis applied to a 6.5% hydroxyethylated commercial agarose yileded a steeper PE vs A plot and also agreement of the above tow models with the data. The PE vs A plot was significantly altered by both further hydroxyethylation and factors that cause variation in the electro-osmosis found in commercial agarose.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280811
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 156
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280901
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 157
    Electronic Resource
    Electronic Resource
    Time-resolved synchrotron radiation x-ray solution scattering study of DNA melting (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1505-1514 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Time resolved x-ray solution scattering measurements were made during thermal denaturation of DNA from various sources in the temperature range of 20-90°C. Preliminary results on the influence of fragement length, ionic strength, and origin of the DNA on the time course of the scattering are described. Interpretation is based on model calculations of the scattering patterns. The resluts indicate that, for long DNA fragments at very low ionic strength, the melting process is a continuous phenomenon over the whole temperature range. It is accompanied by a progressive decrease of the radius of gyration of the cross section and of the mass per unit length. For short fragments of 146 base pair nucleosomal core DNA, stiffening of the DNA appears to precede a sharp melting transition.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280903
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 158
    Electronic Resource
    Electronic Resource
    Local dynamics in biological macromolecules (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1527-1540 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The diffusive approach in the optimized Rouse-Zimm approximation to segment relaxation in the nanosecond time domain (ORZLD) is extended to consider chains of nonequivalent units as occurring in biological macromolecules. The correlation times for second-order time correlation functions of each virtual bond on the chain are calculated for some homopolypeptides, and random and regular copolypeptides. The expected correlation times for biological macromolecules organized in multiple domains are discussed via a simple model of the ORZLD hierarchy. Dynamic bond correlation times are compared with static local presistence lengths.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280905
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 159
    Electronic Resource
    Electronic Resource
    Aggregation of amphotericin B in the presence of γ-cyclodextin (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1585-1596 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The macrolide antibiotic amphotericin B (AmB) forms an inclusion complex with γ-cyclodextrin (γ-CDx), resulting in a molecularly dispersed state of the drug. The state of aggregation of AmB in different solvents has been studied by absorption (uv-vis) and CD spectroscopy. While in aqueous solutions AmB forms colloid-like multimolecular aggregates, in the presence of γ-CDx true solutions can be prepared, which show similar spectral properties as AmB dissolved in organic solvents. The AmB-γ-CDx complex can be isolated as an amorphous, stable, water-soluble powder, indicatin that γ-CDx is a good carrier for the solubilization of this antibiotic. Using γ-CDx as a carrier, the danger of precipitation of the drug during parenteral or intravenous administration can be largely reduced.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280908
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 160
    Electronic Resource
    Electronic Resource
    Orientational dynamics of T2 DNA during agarose gel electrophoresis: Influence of gel concentration and electric field strength (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1541-1571 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The understanding, on a molecular level, of the mechanisms responsible for the improved separation in DNA gel electrophoresis when using modulated electric fields requires detailed information about conformational distribution and dynamics in the DNA/gel system. The orientational order due to electrophoretic migration (“electrophoretic orientation”) is an interesting piece of information in this context that can be obtained through linear dichroism spectroscopy [M. Jonsson, B. Åkerman, and B. Nordén, (1988) Biopolymers 27, 381-414]. The technique permits measurement of the orientation factor S of DNA (S = 1 corresponds to perfect orientation) within an electrophoretic zone in the gel during the electrophoresis. It is reported that the degree of orientation of T2 DNA [170 kilo base pairs (kpb)] is considerable (S = 0.17 in 1% agarose at 10 V/cm) compared to relatively modest orientations of short fragments found earlier (for 23-kbp DNA, S = 0.03 in 1% agarose at 10 V/cm), showing that large DNA coils are substantially deformed during the migration. Growth and relaxation dynamics of the orientational order of the T2 DNA are also reported, as functions of gel concentration (0.3-2%), electric field strength (0-40 V/cm), and pulse characteristics.The rise profile of the DNA orientation, when applying a constant field, is a nonmonotonic function that displays a pronounced overshoot, followed by a minor undershoot, before it reaches steady-state orientation (after 12 s in 1% agarose, 9 V/cm). The orientational relaxation in absence of field shows a multiexponential decay in a time region of some 10 s, when most of the DNA anisotropy has disappeared. A surprising phenomenon is a memory over minutes of the DNA/gel system to previous pulses: with two consecutive rectangular pulses (of the same polarity), the orientational overshoot and undershoot as a response to the second pulse are significantly reduced compared to the first pulse. The time required to recover 90% of their amplitudes is typically 1200 s (1% agarose, 9 V/cm), which may be compared to the time required to relax 90% of the DNA orientation, which is only 6 s. The major part of the over- and undershoot recovery is thus a reorganization of a system in which DNA is already randomly oriented.The different response amplitudes and relaxation times, including the amplitude and recovery time of the overshoot, of the orientational order of DNA in the electrophoretic gel have been studied as functions of gel concentration and field strength. The results are discussed against relevant theories of polymer dynamics.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280906
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 161
    Electronic Resource
    Electronic Resource
    CD and small-angle x-ray scattering of silk fibroin in solution (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1613-1624 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We investigated the structure of silk fibroin dissolved in water and in water-organic solvent mixtures by CD and small-angle x-ray scattering (SAXS). CD spectra indicated a disordered secondary structure in water and a β-sheet conformation in aqueous organic solvents, such as methanol, dioxane, and trifluoroethanol (in trifluoroethanol a transient form evolving toward β-sheet conformation was seen just after dissolution). The SAXS technique indicated the presence of fibroin particles of lamellar shape. The molecular weight was 188,000 daltons in water and 302,000 daltons in aqueous methanol.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280910
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 162
    Electronic Resource
    Electronic Resource
    A temperature-dependent Z to B to single-strand transition in d(CGCG) (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1625-1636 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A thermally induced left- to right-handed helical interconversion for the self-complementary tetradeoxynucleotide d(CGCG) has been observed in the presence of NaCl at concentrations from 1.5 to 2.25M. Analysis of the Raman spectrum of d(CGCG) in aqueous solution as a function of temperature indicates that at low temperature a left-handed Z-helical form is the predominant species. An increase in temperature results in a decrease in the population of the left-handed form and an increase in the population of the right-handed form. Further elevation in temperature results in extensive disruption of base stacking and a loss of secondary structure. This unstacking presumably represents dissociation to a single-stranded structure. The data suggest that a temperature-dependent Z to B to single-strand transition occurs under the conditions employed. A direct Z to single-strand conversion was not identified. In contrast to previous examples, the thermally induced left- to right-handed helical conversion for d(CGCG) can occur in the absence of chemically modified nucleic acid bases, alcohol solutions, or divalent ions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280911
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 163
    Electronic Resource
    Electronic Resource
    On the cooperative binding of large ligands to a one-dimensional homogeneous lattice: The generalized three-state lattice model (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1637-1643 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present the general secular equation for three-state lattice models for the cooperative binding of large ligands to a one-dimensional lattice. In addition, a closed-form expression for the isotherm is also obtained, that can be used with all values of the cooperativity parameter ω(0 〈 ω 〈 ∞) thus eliminating the need for multiple equations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280912
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 164
    Electronic Resource
    Electronic Resource
    Protein complexation with DNA phosphates as a cause for DNA duplex destabilization: A thermodynamic model (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1653-1665 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexation of positively charged sites in a protein with the negative DNA phosphate groups shields the phosphate charges. This diminishes interstrand electrostatic repulsions, which stabilizes the duplex. When phosphate shidlding is present in one DNA strand only, the conformation of this strand changes due to a decrease of intrastrand phosphate-phosphate repulsions. This destabilizes the duplex since then the strands differ in conformation. A thermodynamic model is formulated to describe this stabilization/destabilization effect in terms of changed enthalpies and entropies of hybridization. It is found that protein complexation with one DNA strand can indeed lower the TM value of a duplex. The model is applied to the action of helicases (replication), RNA polymerases (transcription), and restriction endonucleases. Mechanisms with unilateral charge shielding are proposed for their duplex-destabilizing properties.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281002
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 165
    Electronic Resource
    Electronic Resource
    Theory of cooperative transitions in protein molecules. I. Why denaturation of globular protein is a first-order phase transition (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1667-1680 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A theory of equilibrium denaturation of proteins is suggested. According to this theory, a cornerstone of protein denaturation is disruption of tight packing of side chains in protein core. Investigation of this disruption is the object of this paper. It is shown that this disruption is an “all-or-none” transition (independent of how compact is the denatured state of a protein and independent of the protein-solvent interactions) because expansion of a globule must exceed some threshold to release rotational isomerization of side chains. Smaller expansion cannot produce entropy compensation of nonbonded energy loss; this is the origin of a free-energy barrier (transition state) between the native and denatured states. The density of the transition state is so high that the solvent cannot penetrate into protein in this state. The results obtained in this paper make it possible to present in the following paper a general phase diagram of protein molecule in solution.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281003
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 166
    Electronic Resource
    Electronic Resource
    Effects of chloroquine on the torsional dynamics and rigidities of linear and supercoiled DNAs at low ionic strength (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1695-1703 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The magnitude and uniformity of the torsion elastic constant (α) of linear and supercoiled pBR322 DNAs are measured in 3 mM Tris as a function of added chloroquine/basepair ratio (chl/bp) by studying the fluorescence polarization anisotropy of intercalated ethidium dye. The time-resolved FPA is measured using a picosecond dye-laser for excitation and time-correlated single-photon counting detction. For both linear and supercoiled DNAs, α remains uniform except at the very highest chl/bp ratio examined. For the linear DNA, α decreases from 5.0 × 10-12 dyne-cm at chl/bp = 0 to about 3.5 × 10-12 dyne-cm at chl/bp = 0.5, and remains at that value up to chl/bp = 5, whereupon it increases back up to its original value. For the supercoiled DNA, α remains constant at about 5.2 × 10-12 dyne-cm from chl/bp = 0 up to chl/bp = 5, whereupon it increases in parallel with the linear DNA. The effect of chloroquine on the secondary structure, torsion constant, and torsional dynamics evidently differs substantially between linear and supercoiled DNAs, even under conditions where the supercoiled DNA is completely relaxed and both DNAs bind the same amount of dye. This strongly contradicts any notion that the local structures of linear and relaxed supercoiled DNA/dye complexes with the same binding ratio are identical. The increase in apparent α at chl/bp = 5 for both DNAs may be due to stacking of the chloroquine in the major groove and consequent stiffening of the filament.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281005
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 167
    Electronic Resource
    Electronic Resource
    Conformational transitions of leucine-containing isomeric sequential basic polytripeptides (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1731-1744 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational transitions of basic sequential polytripeptides (Lys-Ala-Leu)n, (Arg-Ala-Ala)n, (Arg-Leu-Ala)n, and (Arg-Ala-Leu)n, induced by elevated salt concentrations and/or temperatures in aqueous solutions, were investigated by CD, sedimentation equilibrium, and viscometry. The behavior of (Lys-Ala-Leu)n was compared with that of the sequential isomer (Lys-Leu-Ala)n, studied previously. It was found that both polypeptides are highly helical with a tendency to aggregate in high salt solutions. Although the hydrophobic interactions between Lys and Leu residues play an important role in both cases, the final effect on helix stabilization and aggregation is different. The Arg-containing polypeptides were found to assume the α-helical conformation. Compared to the Lys-containing polypeptides (Lys-Ala-Leu)n and (Lys-Leu-Ala)n, a very low tendency to aggregate was observed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281007
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 168
    Electronic Resource
    Electronic Resource
    IR vibrational CD in alanyl tripeptide: Indication of a stable solution conformer (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1759-1770 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared vibrational CD (VCD) of a small peptide, L-alanyl-L-alanyl-L-alanine (Ala3), and a peptide model, N-acetyl-L-alanine-N′-methyl-amide (AAMA), in the 1550-1750-cm-1 region has been observed. The “coupled oscillator” VCD feature observed for Ala3 in the amide I region is interpreted in terms of a solution structure stabilized by the electrostatic interaction of the zwitterionic groups. No such interactions are possible in basic aqueous solution of Ala3 nor in AAMA in neutral solution. Thus, the coupled oscillator features are lost in the latter two cases, indicating the absence of a simple stabilized conformation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281009
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 169
    Electronic Resource
    Electronic Resource
    Solution conformation of the actinomycin D related pentapeptide lactone using nmr and molecular modeling (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1771-1780 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A detailed description of the two observed solution conformations of the pentapeptide lactone fragment of actinomycin D is presented using the distance constraints obtained from two-dimensional nuclear Overhauser enchancement spectra in combination with minimum energy calculations. Low energy conformational states that are compatible with the experimental distances are found for each of the two conformers. For one conformer, an all trans peptide bond conformation is found with no intramolecular hydrogen bonds. For the other conformer, the D-Val-Pro and Pro-Sar peptide bonds were cis; this solution conformation is the same as that found in both the crystal structure of the pentapeptide lactone as well as of the native actinomycin D itself. These results are discussed in terms of the combined influence of conformation and the effects of mutual intramolecular association of the pentapeptide lactone moieties in native actinomycin D on its cytotoxic activity.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281010
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 170
    Electronic Resource
    Electronic Resource
    DNA gel electrophoresis: Effect of field intensity and agarose concentration on band inversion (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1793-1799 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We study the effect of electric field intensity and agarose gel concentration on the anomalous electrophoretic mobility recently predicted by the biased reptation model and experimentally observed for linear DNA fragments electrophoresed in continuous electric fields. We show that high fields and low agarose concentrations eliminate the physical mechanism responsible for anomalous DNA mobility and band inversion, in good agreement with theory, thus restoring the monotonic mobility-size relationship necessary for unambiguous interpretation of the results of DNA gel electrophoresis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281012
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 171
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281101
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 172
    Electronic Resource
    Electronic Resource
    Vibrational free energy, entropy, and temperature factors of DNA calculated by a helix lattice approach (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1841-1860 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vibrational contribution to the free energy, entropy, and the temperature factors of the different atoms in the unit cell are calculated using the method of helix lattice dynamics for the DNA homopolymer poly(dG · poly(dC)) in the B conformation. These results are compared to other theoretical calculations and the temperature (B) factors are compared to experiment as well. The problems encountered in using small molecule approximations to describe B factors in DNA like long chain molecules are discussed and a corrected estimate of the temperature factors are presented. Significant differences are found between the different theoretical approaches as reflected in the results of temperature factor calculations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281102
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 173
    Electronic Resource
    Electronic Resource
    Dielectric relaxation in synthetic melanin (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1875-1883 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The charging and discharging currents were investigated in a synthetic melanin sample. The presence of long-lasting dielectric relaxation was established. The steady state was reached after a long time, from 103 to 105 s, which depends both on temperature and voltage.The temperature dependence of polarization was of an activation character (Eα = 0.67 eV). The kind of electrode material did not influence the current curves.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281104
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 174
    Electronic Resource
    Electronic Resource
    I - V characteristics and electrical conductivity of synthetic melanin (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1885-1890 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: I - V characteristics for synthetic melanin were investigated at - 10 and 25°C. It was found that the Ohm law is valid for low voltages whereas the Child law holds for higher ones. Furthermore, the steady state electrical conductivity was estimated. The change of activation energy from 0.76 eV for low temperatures to 1.58 eV was noticeable near 0°C.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281105
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 175
    Electronic Resource
    Electronic Resource
    Glycosaminoglycan conformations and changes on periodate oxidation (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1891-1902 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The progressive periodate oxidation of glycosaminoglycans (GAG), including hyaluronate (HA), chondroitins (CH) (chondroitin, chondroitin 4- and 6-sulfate), dermatan sulfate (DS), and keratan sulfate (KS), were monitored by CD and high performance liquid chromatography (HPLC) using a size-exclusion column. The rate of oxidation also was measured and calculated using first- and second-order kinetics, and the data appear to fit better with first-order kinetics. In both HA and CH, the n - π* amide band at 208 nm decreases in intensity upon oxidation, but in HA it becomes positive after 16 h of periodate treatment. In CH, the band disappears, and the π - π* amide band below 200 nm becomes optically active. Concomitantly, a second negative band near 290 nm appears for these two oxidized GAG. Oxidation causes a slight change in the CD of DS. It ordinarily displays a very weak n - π* band at 210 nm, but instead shows an intense π - π* amide band near 190 nm. CD of KS remains unaffected by periodate. Kinetic studies, however, show a higher oxidation rate for DS than HA and CH. With the exception of KS, all other oxidized polymers shown an apparent decrease in molecular weight (higher peak retention time) in HPLC analysis. Both CD and HPLC results have been attributed to a major conformational cahange of HA and CH, and a minor one for DS. The ease and extent of periodate oxidation as well as the changes in molecular properties following periodate treatmenat are critically dependent on the changes in molecular properties following periodate treatment are critically dependent on the configuration of the individual GAG rather than the oxidation rate. There is a distinct difference in the conformational change between HA and CH, as manifested by their dichroic behavior, that was attributed to the equatorial disposition of C-4 hydroxyl group in HA and axial disposition CH.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281106
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 176
    Electronic Resource
    Electronic Resource
    A Monte Carlo simulation study of the influence of internal motions on the molecular conformation deduced from two-dimensional nmr experiments (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1903-1911 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monte Carlo methods have been used to simulate internal motions of aromatic protons of an oligonucleotide at the nanosecond time scale. Each proton is allowed to fluctuate about its equilibrium position. The longitudinal cross-relaxation rates of such a system of spins have been determined by computing the appropriate correlation functions. Then the interproton distances have been deduced according to the procedure generally used in two-dimensional nmr techniques (nuclear Overhauser effect spectroscopy - NOESY) and compared to the true values. The influence of the amplitude A and of the internal rotational diffusion constant Dint characterizing the dynamics of the system has been checked for in-phase and for uncorrelated motions. It is shown that for the investigated models the distances deduced from NOESY experiments may be under or overestimated, depending strongly on the values of A and Dint. Furthermore, the cross-relaxation rate of a couple of protons is very sensitive to the correlation level of the motions of both protons.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281107
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 177
    Electronic Resource
    Electronic Resource
    Masthead (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720101
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 178
    Electronic Resource
    Electronic Resource
    The Conformation of Cycloartenol Investigated by NMR and Molecular Mechanics (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1-13 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloartenol (4), a natural plant sterol, was shown to be an effective membrane reinforcer; this was attributed to its conformation. We now present a conformational analysis of 4 by molecular modeling and NMR. Molecular modeling suggests that two conformations I and II coexist, differing mainly at the level of ring C, and of nearly equal energy, I and II each having ring A and B in a chair and half-chair conformation, respectively, with ring C 1,3-diplanar in I (solid-state structure as determined by X-ray crystallography) and in chair conformation in II. A complete assignment of the 1H- and 13C-NMR spectra of 4 and the entire coupling network in rings A and B is determined by various modern NMR techniques. The conformation of rings A and B thus determined is in agreement with conformations I and II. Low-temperature NMR experiments show a fast equilibrium between two conformations, presumably I and II. It is concluded, therefore, that the cyclopropane ring of 4 produces a flexibility at the level of ring C which may be important for the membrane properties.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720102
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 179
    Electronic Resource
    Electronic Resource
    Palladium(0)-Catalyzed Cyclizations of Simple 1-Aryl-1,7-octadien-3-yl Acetates. Preliminary communicationPresented (W.O.) at the ‘3e Congrès national de la Société Française de Chimie’, Nice, September 5, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 14-16 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dienyl acetates 2 lacking a geminal disulfone or a malonate group cyclize selectively to (E)-l-methylidene-2-styrylcyclopentanes 4 in the presence of 7 mol-% of [Pd(PPh3)4].
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720103
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 180
    Electronic Resource
    Electronic Resource
    Über den Einfluss des Akzeptor-Teilchromophors bei Dimethin-merocyanin-Farbstoffen auf das Aggregationsverhalten in wässriger Lösung (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 17-28 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Influence of the Acceptor Part of the Chromophor of Dimethinemerocyanine Dyes upon the Aggregation Tendency in Aqueous SolutionA series of novel long-chain alkyl-dimethinemerocyanine dyes containing sulfonate groups is synthesized in good yield and their aggregation tendency in H2O and in organic solvent/H2O mixtures investigated. The merocyanine dyes 11 and 15 only exhibit an intense, red-shifted absorption band due to J-aggregation in H2O without addition of salt. The influence of cationic and anionic tensides and other compounds as urea, glucose, and polysaccharides upon the J-aggregation tendency is investigated.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720104
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 181
    Electronic Resource
    Electronic Resource
    Generation and Trapping of TriafulveneFulvene, Fulvalenes, Part 55; Part 54: [1].Short communication: [2]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 29-40 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted methylidenecyclopropanes 12a-d, being easily available from 1,1-dibromo-2-(phenylthio)-cyclopropane (9a), are attractive precursors of triafulvene (2-methylidene-1-cyclopropene; 1). Both the sulfoxide 12b and the sulfone 12c react with an excess of alkoxides (t-BuOK and NaOMe) to give 12e and 12f, respectively, while the sulfinyl group of 12b may be replaced by the PhCH2S substituent in the presence of PhCH2SH/t-BuOK. These reactions (Scheme 4) may be explained by assuming 1 as a reactive intermediate, although an alternative sequence including carbene 20 (Scheme 6) is not completely ruled out. D-labelling experiments (Scheme 5) do not give conclusive evidence due to D scrambling, but deprotonation/methylation sequences show that H—C(2) of 12a-c is the most acidic proton. Final evidence for 1 results from the reaction of 12d with cyclopentadienide (Scheme 7): the reaction of 1 with cyclopentadiene produces the expected [4 + 2]-cycloaddition product 23, while some mechanistic insight results from the sequence 12d → 24 → 25.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720105
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 182
    Electronic Resource
    Electronic Resource
    A Nonconcerted Intramolecular Diels-Alder Reaction of Chiral Allenic-Acid Derivatives (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 59-64 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction between the chiral allenic acid (+)-(S)-1 and the carbodiimides 2a-d and the keten-imine 6 gives, under mild conditions, the tricyclic compounds 3-5, 7, and 8. Low diastereoselectivity and a partial loss of optical activity are observed. A stepwise mechanistic pathway via a biradical intermediate is postulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720108
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 183
    Electronic Resource
    Electronic Resource
    Konkurrenz von Endoperoxid- und Hydroperoxid-Bildung bei der Umsetzung von Singulett-Sauerstoff mit cyclischen, konjugierten Dienen. Teil I (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 51-58 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Competition of Endoperoxide and Hydroperoxide Formation in the Reaction of Singlet Oxygen with Cyclic, Conjugated DienesRose-bengal-sensitized photooxygenation of (-)-(R)-α-phellandrene (1) in MeOH at room temperature yielded a complex mixture of products, contrary to previous reports describing cis-(3S, 6R)-epidioxy-p-menthene (2) and trans-(3R, 6S)-epidioxy-p-menthene (3) as the only products. The mixture was separated by prep. HPLC (silica gel, pentane/Et2O 9:1). Besides the known endoperoxides 2 (yield 39%) and 3 (26%), all those hydroper-oxides, which can be deduced from an ene reaction of 1O2 with 1, were isolated, i.e. 4β-p-mentha-2,5-dien-1β-yl hydroperoxide (4) (14%), 4β-p-mentha-2,5-dien-1α-yl hydroperoxide (5) (9%), (2R, 4R)-p-mentha-1(7), 5-dien-2-yl hydroperoxide (6) (2,1%), (2S, 4R)-p-mentha-1(7),5-dien-2-yl hydroperoxide (7) (1,5%) and (1R)-p-mentha-3,6-dien-yl hydroperoxide (8; 1,5%; Scheme 1). Furthermore, the constant cis/trans ratio for all diastereoisomeric pairs (2/2, 4/2, 6/2) was striking. With the help of the two possible conformers 1a and 1b of the starting material a model of a common first step for endoperoxide as well as for hydroperoxide formation is developed. A photooxygenation at -50° supports this model. The absolute value of the cis/trans ratio changes in the same way for the endoperoxides and the hydroperoxides.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720107
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 184
    Electronic Resource
    Electronic Resource
    Versuche zur Synthese von Calicen aus trisubstituierten Cyclopropanen und Cyclopentenon56. Mitt. über Fulvene, Fulvalene; 55. Mitt. [1]: Kurzmitt. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 41-50 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempted Synthesis of Calicene from Trisubstitued Cyclopropanes and CyclopentenoneThe Li carbenoids 4, prepared by treatment of substituted 1,1-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a-e, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C(1) of cyclopent-2-enone, while 4a (Y = PhS) predominantly deprotonates the ketone (Scheme 4). Whereas 5d and 5e can easily be converted to the dihydrocalicenes 6d and 6e (Scheme 6), the attempted elimination of H2O from 5a-c leads to the rearranged products 13-2 due to the opening of the cyclopropane ring (Scheme 5). Finally, the generation of the parent compound 2 from the silylated precursor 6d is attempted: treatment with MeO- gives the addition products 18A/18B, while the reaction with Br2 provides 19 by a bromination/dehydrobromination sequence (Scheme 7).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720106
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 185
    Electronic Resource
    Electronic Resource
    Locoselective [4 + 2] Cycloadditions of Vinylindoles with Inverse Electron Demand: A new access of indolyl-substituted and annellated pyridazinesDedicated to Prof. Dr. C. H. Brieskorn (Würzburg, FRG) on the occasion of his 75th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 65-72 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Vinylindole (1a) and its donor- and acceptor-substituted (E)-derivatives 1b-e react highly locoselectively with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (3) to form the novel (indol-2-yl)-1,4-dihydropyridazines 4a and 7 as well as the heterocyclic annellated pyridazines 4b, 5, and 6. The reactions of the structurally related 3-vinylindoles 2a-e with 3 also gave rise to new indol-3-ylpyridazines 8, 9, and 10. The locoselectivities of these Diels-Alder reactions were controlled mainly by steric effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720109
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 186
    Electronic Resource
    Electronic Resource
    Photochemistry of Thiophen-2(5H)-onesDedicated to Prof. Dr. O. E. Polansky on the occasion of his 70th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 83-92 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanistic evidence for the light-induced ring opening of thiophen-2(5H)-ones 1 in alcohols affording α, β-unsaturated mercapto esters 2 is presented. Regio-and stereochemical aspects of the ring closure of alkenylthio (type 3) radicals 15 and 17 to S-heterocycles 16 and 18, of 3-thiahex-5-enyl radicals 4 to (tetrahydrothien-3-yl)methyl radicals 6 and of (2,3-dihydrothien-3-yl)methyl radicals 30 (type 7, but-3-enyl radicals) to cyclopropane-methyl radicals 29 are discussed. Irradiation (λ 350 nm) of 1 in cyclohexane in the presence of 2,3-dimethylbut-2-ene affords [2 + 2] cycloadducts 14 albeit in very low yields.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720111
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 187
    Electronic Resource
    Electronic Resource
    Electronic and Molecular Structure of the C8H10+· Valence Isomers 1,3,5-Cyclooctatriene+· and Bicyclo[4.2.0]octa-2,4-diene+· from their Electronic absorption Spectra in Freon (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 73-82 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular cations of 1,3,5-cyclooctatriene (COT+·) and bicyclo[4.2.0]octa-2,4-diene (BCO+·) can be observed intact in γ-irradiated Freon glasses, as opposed to Ar matrices where ionization is accompanied by extensive rearrangements. This proves the superiority of the Freon-glass method for the generation of metastable primary cations. The electronic absorption (EA) spectra reveal a) that a previous analysis of the BCO+· electronic structure on the basis of the ultraviolet photoelectron (UP( spectrum of BCO was incomplete, and b) that COT undergoes planarization upon ionization, in accord with qualitative expectations and MNDO calculations. A previously proposed LCBO model was used to assess the influence of the above geometry change on the electronic structure of COT+·.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 188
    Electronic Resource
    Electronic Resource
    Cyclization Studies with N-Mannich bases of 2-substituted indoles (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 93-100 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the indoles 7, 15, 16 with a 3-methoxyphenyl group, attached via an α-side chain of 1,2,or 3 CH2 units, is reported. These compounds, after appropriate protection at C(3), were transformed into the N-[(dimethylamino)methyl]indoles 22, 23, and 24, respectively. When treated with AcCl, these N-Mannich bases gave, in two cases, stable N-(chloromethyl)indoles 25 and 26. In the presence of SnCl4, ring closure occurred via electrophilic attack of 1-methylideneindolium ions on the methoxyphenyl group. Formation of seven-membered rings (→ 27, 28) and eight-membered rings (→ 29) was found to be a favorable process. Cyclization to six-membered rings did not occur within this series.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720112
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 189
    Electronic Resource
    Electronic Resource
    Template-Dependent Incorporation of Spin-Labeled Thymidine Analogs into Viral DNA (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 110-116 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel pppUd analogs substituted at position C(5) with tethered nitroxide radicals is reported. It is shown that these analogs can serve as good substrates for E. coli DNA polymerase (Pol I) and T-4 DNA polymerase using lambda-phage DNA as template. The template-dependent incorporation of the substrates was established by radio-labeling and ESR experiments.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720114
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 190
    Electronic Resource
    Electronic Resource
    Stereoselektive Synthesen von Taxan-Derivaten (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 101-109 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective Synthesis of Taxane DerivativesSubstituted racemic 4,8,12-trinortaxanes were prepared stereoselectively in several steps from the dienone 10. A variant of the de Mayo reaction with bicyclononenones 4 and cyclohexen produced the desired configuration at C(8) of the taxane framework. Retro-aldol cleavage of the tetracycle 5 led to the taxane skeleton 6. Stereoselective reduction followed by treatment with base afforded 7b. Hydrolysis of the acetal group and further reduction yielded 9 in which the relative configuration corresponds to the one of the natural products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720113
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 191
    Electronic Resource
    Electronic Resource
    Asymmetric Diels-Alder reactions: X-Ray crystal-structure analysis of [N-((E)-But-2-enoyl)bornane-10,2-sultam]tetrachlorotitaniumPresented (WO) at the Annual Congress of the Royal Society of Chemistry, Canterbury, April, 1988. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 123-130 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An X-ray diffraction analysis of the crystalline complex 2b (MLn — TiCl4) shows a chelation of the carbonyl O-atom and the upper SO2 O-atom by TiCl4, a slightly pyramidal N-atom, and a π -face-stereoselective shielding of the C(α)-Si face by the CH2(3) group. The Ti-atom is in a pseudo-octahedral environment.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720116
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 192
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands. Part XXVIIPart XXVI. Cu2+-promoted hydrolysis of carboxylic- and phosphonic-acid esters in the side chain of tetraazamacrocycles (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 131-138 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray structures of the Cu2+ complexes of 1,4,8,11-tetraazacyclotetradecane derivatives with an ethylpro-pionate and diethylphosphonate group, 5 and 6, respectively, indicate that the metal ion is pentacoordinated by the four N-atoms of the macrocycle and one O-atom. In the case of 5, it is the carbonyl O-atom of the carboxylate group, whereas for 6 it is the phosphonyl O-atom of the phosphonate group. The hydrolysis kinetics of the functional group in the Cu2+ complexes with the 1,4,8,11-tetraazacyclotetradecanes 3-6 have been measured by pH-stat and stopped-flow techniques. The rate law for the hydrolysis of the carboxylates 3-5 is proportional to the complex concentration and to [OH-] up to pH 13, whereas that of the phosphonate 6 is proportional to [OH-] up to pH 11.5, becoming independent of [OH-] at pH 〉 11.5. The mechanisms of these two reactions are discussed, considering the possibility of an intra- or an intermolecular OH- attack and the results of the X-ray structure analyses.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720117
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 193
    Electronic Resource
    Electronic Resource
    A New Method for the Preparation of (E)-3-Acylprop-2-enoic AcidsPresented in part at the autumn meeting of the Swiss Chemical Society in Bern on October 21, 1988.Dedicated to Prof. R. E. Ireland on the occasion of his 60th birthday (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 117-122 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method for the preparation of (E)-3-acylprop-2-enoic acids ( = (E)-3-acylacrylic acids) of type II via acid-catalyzed isomerization of the corresponding 3-acylprop-2-ynal acetals of type I (Scheme 1) has been found. The described reaction gives a rapid and quite general access to these compounds known to exhibit a number of interesting biological activities. Some studies toward the elucidation of the reaction mechanism have been made, and a hypothetical mechanism is proposed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720115
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 194
    Electronic Resource
    Electronic Resource
    6-Thia-1-aza-5λ5-phosphabicyclo[3.2.0]hept-3-ene und Isothiocyanatophosphin-sulfide aus (Methylidenamino)phosphinen, Schwefelkohlenstoff und Acetylen- oder Ethylen-Derivaten (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 139-146 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 6-Thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes and Isothiocyanatophosphine-sulfides from (Methylidenamino)phosphines, Carbon Disulfide, and Acetylene- or Ethylene Derivatives(Methylidenamino)phosphines react with carbon disulfide to 1,3,2-thiazaphosphete derivatives 2. Acetylenedicarboxylates give with 2 6-thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes 4a, b, and acrylates yield isothio-cyanatophosphin-sulfides 5a-c. The structures of 4a and 5a are proven by an X-ray diffraction analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720118
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 195
    Electronic Resource
    Electronic Resource
    C45 und C50-Carotinoide. 6. Mitteilung5. Mitteilung, s. [1]. Synthese eines optisch aktiven cyclischen C20-Bausteins und von Decaprenoxanthin (= (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotin) (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 151-157 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: C45- and C50-Carotenoids: Synthesis of an Optically Active Cyclic C20-Building Block and of Decaprenoxanthin ( = (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotene)The synthesis of the optically active cyclic C20-building block (R, R)-15 and of the optically active C50-carotenoid (2R, 6R, 2′R, 6′R)-decaprenoxanthin (1) starting from (-)-β-pinene ((S)-2) is reported.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720120
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 196
    Electronic Resource
    Electronic Resource
    Formation of the First Trimeric Monoterpenoid Indole Alkaloids (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 147-150 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under O2, the Aspidosperma alkaloid tabersonine (1) was converted by a crude enzyme preparation from leaves of mature plants of Catharanthus roseus G DON into the trimeric 3-hydroxy-14′-(3α″-tabersonyl)voafrine B (4) which was easily reduced by NaBH4 to 14′-(3α″-tabersonyl)voafrine B ( = tertabersonine; 5). Compounds such as 4 and 5 are the first trimeric alkaloids in the series of monoterpenoid indole alkaloids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720119
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 197
    Electronic Resource
    Electronic Resource
    Polynuclear Iron and Rhodium Complexes of 7-Oxa[2.2.1]hericene (2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one) (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 158-164 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: μ-Carbonyl(Rh—Rh)di(η5-indenyl)[(2R,3S)-C,2,3,C-η-(2,3,4,5-tetramethylidenebicyclo[2.2.1]heptan-7-one)]]-dirhodium(I)(Rh—Rh) (7) and cis-μ-[(2R,3S,5R,6S))-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis[μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)] (8) have been prepared. Complex 7 reacts with Fe2(CO)9 in hexane/MeOH and gives cis-μ-[(2R,3S,5R,6S] (9), trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η: C,5,6, C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)-μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)-(tricarbonyliron) (10), and, μ-carbonyl(Rh—Rh)[(2R,3S)-C,2,3,C-η-(2,3-dimethyl-5,6-dimethylidenebicyclo-[2.2.1]hept-2-en-7-one)]di(η5-indenyl)dirhodium(I)(Rh—Rh) (11). Treatment of 7-oxa[2.2.1]hericene (4) with Fe2(CO)9 or (cyclooctene)2Fe(CO)3 gave a 1:2 mixture of cis-μ-[(2R,3S,5R,6S)-] (12) and trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis(tricarbonyliron)(13).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720121
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 198
    Electronic Resource
    Electronic Resource
    Eine neue Aminoazirin-Reaktion. Bildung von 3,6-Dihydropyrazin-2(1H)-onen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 172-179 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Aminoazirine Reaction. Formation of 3,6-Dihydropyrazin-2(1H)-onesThe reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethyl)-1,3-oxazol-5(2H)-ones 5 in MeCN or THF at 50-80° leads to 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 6 (Scheme 3). Reaction mechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH-acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via intermediate formation of N-(trifluoroacetyl)dipeptide amide 8 (Scheme 5) is excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720123
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 199
    Electronic Resource
    Electronic Resource
    Synthesis of the Oviposition-Deterring Pheromone (ODP) in Rhagoletis cerasi L. Preliminary communication (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 165-171 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the assignment of the configuration at C(8) and C(15) of the natural oviposition-deterring pheromone 1 in Rhagoletis cerasi L., the four possible stereoisomers of 1 are synthesized. By condensing the C6 building blocks (5R)-4 and (5S)-4 with the boron enolates of the C10 building blocks (4S)-13 and (4R)-13, followed by decarboxylative dehydration, all stereoisomers of 16 are available (Scheme 5). Glucosylation of 16 followed by formation of the taurin amide gives, after deprotection, the four stereoisomers (8R,15S)-1, (8R,15R)-1, (8R,15S)-1, and (8S,15S)-1 (Scheme 6).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720122
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 200
    Electronic Resource
    Electronic Resource
    Mitteilungen (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 185-192 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720125
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...