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  • 1985-1989  (29)
  • 1920-1924
  • 1988  (29)
  • Chemistry  (26)
  • Computational Chemistry and Molecular Modeling  (3)
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  • 1985-1989  (29)
  • 1920-1924
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  • 1
    Electronic Resource
    Electronic Resource
    Alkali-triazaphosphininolate  -  Darstellung und Reaktionen (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 1119-1121 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alkali Triazaphosphininolates  -  synthesis and ReactionsThe alkali triazaphosphininolates 2, 3, 4, and 6 are obtained by the reaction of 2,2-difluoro- or 2,2-dichloro-4,6-bis(trifluoromethyl)-1,3,5,2λ5-triazaphosphinine (1 and 5) with NaOCHMe2, NaOCMe3, KOCHMe2, or KOCMe3 and LiOSiMe3. NaOSiMe2CMe3 reacts with 1 in a molar ratio 1:1 or 2:1 to give the siloxy-substituted compounds 8 and 92). The 2-fluoro-triazaphosphinin-2-ol 72) is formed in the reaction of 4 with HF. 7 reacts with KOH to yield 2. The reaction of the sodium triazaphosphininolate 3 with ClSiMe3 leads to the formation of the siloxytriazaphosphinine 10. The N-lithiotriazaphosphinine-2-amines 13 and 14 are obtained from the aminofunctional compounds 11 and 12 and LiN(SiMe3)2. 14 reacts with ClSiMe3 to give LiCl and 15.
    Notes: Die Alkali-triazaphosphininolate 2, 3, 4 und 6 werden durch Reaktion von 2,2-Difluor- bzw. 2,2-Dichlor-4,6-bis(trifluormethyl)-1,3,5,2λ5-triazaphosphinin (1 bzw. 5) mit NaOCHMe2, NaOCMe3, KOCHMe2 oder KOCMe3 sowie mit LiOSiMe3 erhalten. NaOSiMe2CMe3 reagiert mit 1 im molaren Verhältnis 1:1 bzw. 2:1 zu den Siloxyverbindungen 8 und 9. Das 2-Fluor-triazaphosphinin-2-ol 7 entsteht aus 4 und HF. 7 kann mit KOH in 2 übergeführt werden. Natrium-triazaphosphininolat 3 reagiert mit ClSiMe3 zum Siloxy-triazaphospininolat 10. Die N-Lithio-triazaphosphinin-2-amine 13 und 14 entstehen aus den aminofunktionellen Verbindungen 11 und 12 mit LiN(SiMe3)2. 14 reagiert mit ClSiMe3 zu LiCl und 15.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210616
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  • 2
    Electronic Resource
    Electronic Resource
    Hochsubstituierte 1-tert-Butyl-1-silacyclohexadiene (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 1393-1398 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Highly Substituted 1-tert-Butyl-1-silacyclohexadienesSilacyclohexadienes with bulky ligands and good leaving groups are of interest for experiments concerning the synthesis of kinetically stabilized silabenzene derivatives. Here we describe the synthesis of 1-tert-butyl-1-silacyclohexadienes, which are substituted in 1-, 2-, 4-, and 6-position. From lithiated precursors, the trialkylsilyl- or tert-butyl-substituted silacyclohexadienes 6, 8, 9, 12, 13, 14, and 15 are formed by substitution reactions. The methoxysilane 1 is transferred with LiAlH4 to the hydrosilane 2. Si—H or C—H bond cleavage with N-bromosuccinimide results in the formation of the silacyclohexadienes 3 and 5, brominated in 1- and/or 4-position. In some substitution reactions isomerisation of the diene system is observed. The new compounds are characterized by their 1H-, 13C-, and 29Si-NMR spectra and by their MS data.
    Notes: Mit sperrigen Liganden und guten Abgangsgruppen versehene Silacyclohexadiensysteme sind für Versuche zur Darstellung von kinetisch stabilisierten Silabenzolderivaten von Interesse. Wir berichten hier über Synthesen von in 1-, 2-, 4- und 6-Stellung substituierten 1-tert-Butyl-1-silacyclohexadienen. Aus lithiierten Vorstufen entstehen durch Substitutionsreaktionen die Trialkylsilyl- bzw. tert-Butyl-substituierten Silacyclohexadiene 6, 8, 9, 12, 13, 14 und 15. Das Methoxysilan 1 wird mit LiAlH4 in das Hydridosilan 2 übergeführt. Si—H- bzw. C—H-Spaltung mit N-Bromsuccinimid führt zur Bildung der in 1- und/oder 4-Stellung bromierten Silacyclohexadiene 3 und 5. Bei einigen Substitutionsreaktionen wird eine Isomerisierung des Diensystems beobachtet. Die erstmals beschriebenen Verbindungen sind durch ihre 1H-, 13C- und 29Si-NMR-Spektren sowie durch MS-Daten charakterisiert.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210805
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  • 3
    Electronic Resource
    Electronic Resource
    Construction of linearly independent relativistic symmetry orbitals for finite double-point groups including time reversal symmetry (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 33 (1988), S. 445-465 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A formalism is developed for the construction of relativistic symmetry-adapted molecular basis functions under consideration of time reversal invariance. The theory is applicable to the finite double point groups Cn, Cnh, Sn, Cnv, Dn, Dnd, Dnh, T, Th, Td, O, and Oh. It is based on the LCAO method. A projection operator technique is employed to construct molecular symmetry orbitals from atomic orbitals. The search for linearly independent basis function is simplified by means of group theoretical considerations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560330505
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  • 4
    Electronic Resource
    Electronic Resource
    Arsaphosphenyl- und Diphosphenyl-Komplexe von Chrom und Molybdän (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 559-560 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Arsaphosphenyl and Diphosphenyl Complexes of Chromium and MolybdenumThe reaction of the (pentamethylcyclopentadienyl)(Cp*)-substituted arsaphosphene Cp* As=PAr (2, Ar = 2,4,6-tri-tert-butylphenyl) with M(CO)3(CH3CN)3 (M = Cr, Mo) in toluene affords the novel arsaphosphenyl complexes (η5-C5Me5)(CO)3MAs = PAr (M = Cr: 4; M = Mo: 5) via a transfer of the Cp* ligand from arsene to the metal centre. The corresponding diphosphenyl complex (η5-C5Me5)(CO)3CrP=PAr 3 is obtained analogously from Cp*P=PAr 1 and Cr(CO)3(CH3CN)3. The compounds were characterized by spectroscopic methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210326
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  • 5
    Electronic Resource
    Electronic Resource
    Stereochemistry of Planarchiral Compounds, 11. Static and dynamic stereochemistry of 10,10′-dibromo-2,2′-bi(1,6-methano[10]annulenyl) (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 917-922 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Stereochemie planarchiraler Verbindungen, 11.  -  Statische und Dynamische Stereochemie von 10,10′-Dibrom-2,2′-bi(1,6-methano[10]annulenyl)Bei der Kupplung von 2,10-Dibrom-1,6-methano[10]annulen mit Cu(II)-chlorid (über die Mono-Li-Verbindung) entsteht eine Mischung der meso- und Racemat-Form von 10,10′-Dibrom-2,2′-bi(1,6-methano[10]annulenyl) (2), die durch Chromatographie an Kieselgel getrennt wurde. Die Konfigurationszuordnung der Diastereomeren erfolgte durch 1H- und 13C-NMR-Spektroskopie und durch Racematspaltung. Die Rotationsbarriere von meso-2 wurde durch temperaturabhängige 1H-NMR-Spektroskopie mit 58 kJ mol-1 bestimmt. Nach chromatographischer Enantiomerentrennung von rac-2 in die optisch aktiven Gleichgewichtsmischungen der Rotameren ([α]D = +525 bzw. -525 in Ethanol) konnten diese bei 0°C an Kieselgel (im Verhältnis von 3.6:1) aufgetrennt, ihre CD-Spektren bei -10°C gemessen und die Rotationsbarrieren (85 bzw. 88 kJ mol-1) sowohl durch CD- als auch 1H-NMR-Kinetik (durch Äquilibrierung der Rotameren) bestimmt werden. Die stereochemischen Konsequenzen des Vorliegens von 2 Chiralitätselementen in 2 (Torsions- und Annulen-Chiralität) sowie mögliche Gründe für die (verhältnismäßig) hohe Differenz der Rotationsbarrieren zwischen meso- und Racemat-Form werden diskutiert.
    Notes: Coupling of 2,10-dibromo-1,6-methano[10]annulene with Cu(II) chloride (via the mono-Li derivative) affords a mixture of the meso and racemic forms of 10,10′-dibromo-2,2′-bi(1,6-methano[10]-annulenyl) (2) which were separated by chromatography on silica gel. Their configurational assignments followed from 1H- and 13C-NMR spectroscopy and optical resolution. The rotational barrier of meso-2 was established as 58 kJ mol-1 by temperature-dependent 1H-NMR spectroscopy. After chromatographic resolution of rac-2 into the optically active equilibrium mixtures of the rotamers ([α]D = +525 and -525 in ethanol), they could be separated on silica gel at 0°C (in a ratio of 3.6:1); their CD spectra were recorded at -10°C and the rotational barriers (85 and 88 kJ mol-1, resp.) were established by CD as well as by 1H-NMR kinetics (equilibration of the rotamers). Stereochemical consequences of the presence of two elements of chirality (torsional and annulene chirality) as well as possible reasons for the (relatively) high difference in the rotational barriers for meso and racemic forms are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210515
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  • 6
    Electronic Resource
    Electronic Resource
    Substitution und Isomerisierung an λ5-Triazaphosphininen (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 627-630 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Substitution and Isomerization of λ5-Triazaphosphinines2,2-Difluoro-4,6-bis(trifluoromethyl)-1,3,5,2λ5-triazaphosphinine (1) reacts with CMe3NH2 and MeOH with cleavage of HF to give the substituted compounds 3 and 4. By addition of released HF, the hybrid-ionic compound 5 is formed. A stable 2-fluoro-2-hydroxytriazaphosphinine, N(CCF3N)2PF(OH) (6), is synthesized by the reaction of 1 with CMe3OH, CMe3SiMe2OH, or (CMe3)2Si(OH)2, alkyl fluorides or silyl fluorides being cleaved of. 2,2-Dichlorotriazaphosphinine 2 reacts with (CMe3NH)2SiMe2 to give N(CCF3N)2P(Cl)NHCMe3 (7). N(CCF3N)2P(F)NRSiMe3, R = C6H5 (8), SiMe3 (9), is formed by the reaction of 1 with (Me3Si)2NR. Interaction between 1 and heptamethylsilazane in the molar ratio 1:2 yields the disubstituted product 10 with an exocyclic P=N double bond. The reaction of alkoxides, silanolates, and thiolates with 1 gives mono- (11-17) and disubstituted (18-23) compounds. A migration of methyl and ethyl groups, with formation of an exocyclic P=O bond, is observed (11, 12).
    Notes: 2,2-Difluor-4,6-bis(trifluormethyl)-1,3,5,2λ5-triazaphosphinin (1) reagiert mit CMe3NH2 und MeOH unter HF-Abspaltung zu den Substitutionsverbindungen 3 bzw. 4. Freigesetztes HF addiert an 1 unter Bildung des Zwitterions 5. Das stabile 2-Fluor-2-hydroxytriazaphosphinin N(CCF3N)2PF(OH) 6 entsteht bei der Reaktion von 1 mit CMe3OH, CMe3SiMe2OH und (CMe3)2SiOH)2, wobei Fluoralkan bzw. -silan abgespalten wird. 2,2-Dichlortriazaphosphinin 2 reagiert mit (CMe3NH)2SiMe2 zu N(CCF3N)2(PCl)NHCMe3 (7) und 1 mit (Me3Si)2NR zu N(CCF3N)2P(F)NRSiMe3, R = C6H5 (8), SiMe3 (9). Aus Heptamethyldisilazan und 1 im molaren Verhältnis 2:1 wird ein Disubstitutionsprodukt 10 mit exocyclischer P=N-Bindung isoliert. Alkoholate, Silanolate und Thiolate reagieren mit 1 unter Mono (11-17) und Disubstitution (18-23). Methyl- und Ethylgruppenwanderung, unter Ausbildung einer exocyclischen P=O-Bindung (11, 12), wird beobachtet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210407
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  • 7
    Electronic Resource
    Electronic Resource
    Morphologie der segmentierten polyetheresteramide auf der basis von polyamid 12 und oligotetrahydrofuranHerrn Prof. H.-J. Cantow zum 65. Geburtstag gewidmetVorgetragen anläßlich des Makromolekularen Kolloquiums in Freiburg, 1986. (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 2053-2065 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyetheresteramides (PEEA) on the basis of polyamide 12 and oligotetrahydrofuran (OTHF) may be referred to as intrinsically plasticized and intrinsically impact strength toughened thermoplastic elastomers. This is due to their special 4-phase morphology consisting of two pure crystalline and two mixed amorphous phases, which was completely analysed by various TEM preparation techniques. PEEA containing more than 50% PA 12 hard segments exhibit a space filling dendritic superstructure of lamellar crystallized hard segments. In the range of 50 - 30% PA 12, the dendrites become more and more isolated, and below 30% PA 12 only single lamellae can be observed. The matrix in all PEEA is an amorphous, PA 12-rich mixed phase (“OTHF-plasticized PA 12”) located between the hard segment lamellae. An amorphous OTHF-rich mixed phase is very finely dispersed in PEEA and acts as an intrinsically impact strength toughening modifier. Lamellar crystallized soft segments could be imaged by TEM in this dispersed phase, but only in PEEA products with a higher molecular OTHF and at sufficient low temperatures.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890908
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of crosslink density and internetwork grafting on the transparency of polyurethane/polystyrene interpenetrating polymer networks (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 1467-1473 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Because of their incompatibility and the different refractive indices of the homopolymer components, polyurethane/polystyrene interpenetrating polymer networks are turbid by nature. Different parameters likely to enhance their transparency are examined: the crosslink density of each network and the level of internetwork grafting. The results prove that the latter factor is the most effective, as in some cases, very clear and transparent samples are obtained. Correspondingly, preliminary investigations of the dynamic mechanical properties show an inward shift of the glass transition temperatures for such systems. It is concluded that parameters able to cause a higher degree of phase dispersion can yield transparent materials.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070360616
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  • 9
    Electronic Resource
    Electronic Resource
    Silicone rubber temporomandibular joint (TMJ) meniscal replacements: Postimplant histopathologic and material evaluation (1988)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 22 (1988), S. 475-484 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Medical grade silicone rubber has long been considered a suitable meniscal replacement, but there has been increasing concern about migration of this material into adjacent tissues. The objectives of this study were to determine the definitive composition of tissue-incorporated material which is presumed by light microscopy to be silicone and to identify long term histopathologic sequelae of meniscal replacements. Adult female patients underwent meniscectomy and replacement with silicone rubber (Silastic) implants. After 12 to 18 months, recurrence of symptoms in 8% of these cases led to implant removal with excision of peri-implant fibrous pseudo-capsules. Excised tissues, including one preauricular lymph node and implants were submitted for light microscopy, SEM, and energy dispersive x-ray microanalysis (EDX) for the identification of elemental composition, critical surface tension measurement, and internal reflection infrared spectroscopy. EDX revealed prominent peaks for silicon in both pseudocapsular and nodal tissues. Morphologic findings surrounding the long-term implants included foreign body reaction, synovitis, dystrophic calcification, fibrocartilaginous metaplasia, hyalinization, and scarring. Particulate silicone debris induced a pathologic response in the tissues and migrated to nodes. These findings suggest that periodic evaluation be performed over the life of such implants to rule out breakdown under function. These findings should intensify the search for improvements or replacements for silicone rubber as an interpositional material in the temporomandibular joint.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820220604
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular mechanics and molecular shape. V.For Part IV, see Ref. 1. on the computation of the bare surface area of molecules (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 18-24 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: This article examines the numerical estimation of molecular surface areas within the model of overlapping atomic spheres. One has the choice of either basing the estimate on all elements that contribute to the surface, or of ignoring systematically some elements in the interatomic clefts. It is argued that the second choice, even though more approximate, implicitly improves on the model and is to be preferred. Since surface areas are not measurable, the demonstration is unavoidably roundabout, relying mostly on correlation analysis. Among the regressors occur two compounded parameters. One, ratio of the surface area of the equivalent sphere to the surface area, is interpreted as a measure of molecular globularity. It reflects the molecular axis-ratio and surface convolution. The other, ratio of the surface area to the volume, is interpreted as a measure of the global congestion of a chemical residue. Together with a measure of the local congestion at the point of attachment, it affects the steric hindrance that a residue offers. The relation between the surface area and the number of valence electrons is also discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540090104
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