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
  • 1
    Electronic Resource
    Electronic Resource
    Chemical contrast in scanning near-field optical microscopy (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 675-679 
    Details
    ISSN: 0894-3230
    Keywords: chemical contrast ; scanning near-field optical microscopy ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---Repeatable and stable scanning near-field optical microscopy (SNOM) images are obtained under shear-force control if uncoated, i.e. cold and sharp, tapered fiber tips are used. True chemical contrast is seen for the first time on organic crystals due to the different near-field reflectivities of different chemical species on partly oxidized anthracene. The topography spans a Z-range of 500 nm. The surface roughness is tolerable and the sites of reaction can be related to crystal structure data. A submicroscopic local resolution of 18 nm has been obtained for chemical contrast, discriminating different chemical species even with poorly reflecting organics on rough crystal surfaces. Thus, reflection-back-to-the-fiber SNOM will find wide applications for both transparent and opaque samples. All drawbacks with blunt and hot metal-coated tips at a 〈10 nm distance from the surface in previous SNOM setups are overcome. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Das Fachzeichnen des Metallgewerbes. E. Jachmann und W. Friedrich. Fend. Dümmlers Verlag, Bonn. 1963; 50. und 51.Auflage. DM 6,80 (1964)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 15 (1964), S. 346-346 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19640150420
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Die DIN-gerechte Werkzeichnung. W. Gross und K. Wilhelm. Ferd. Dümmlers Verlag, Bonn. Sept. 1963; 60. bis 63. Auflage. DM 2,80 (1964)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 15 (1964), S. 346-347 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19640150421
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    NMR Chemical-Shift Anomaly and Bonding in Piano-Stool Carbonyl and Related Complexes-an Ab Initio ECP/DFT StudyDedicated to Professor Hans Georg von Schnering on the occasion of his 65th birthday (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 348-358 
    Details
    ISSN: 0947-6539
    Keywords: carbonyl complexes ; density-functional theory ; NMR chemical shifts ; pseudopotentials ; transition-metal complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The origin of the unusually large carbonyl 13C shifts and of unusual periodic trends in four-legged piano-stool complexes [M(n5-C5H5)(CO)4]- (M=Ti, Zr, Hf) and in related species has been investigated by using a combination of ab initio effective-core potentials (ECPs) and density-functional theory (DFT). The ECP/SOS-DFPT(IGLO) calculations indicate a considerable reduction in the anisotropy of the 13C(CO) chemical shift tensors compared to terminal carbonyl ligands in “normal” complexes. This is due to large paramagnetic contributions from metal d AO type (dz2, dxy) orbitals to the parallel component, σ33, of the shielding tensors of the carbonyl carbon atoms. The neutral d4 Group 5 and 6 complexes [M(n5-C5H5)(CO)4] (M=V, Nb, Ta) and [M(n5-C5H5)(CO)3CH3] (M=Cr, Mo, W) exhibit successively smaller but still significant paramagnetic d-orbital contributions to σ33, consistent with the observed less dramatic deshielding. The three-legged d6 piano-stool complexes [M(n5-C5H5)(CO)3] (M=Mn, Tc, Re) do not exhibit these reductions of the shielding anisotropy, but have carbonyl 13C shift tensors comparable to regular octahedral carbonyl complexes. The special situation for the four-legged complexes is related to the presence of high-lying occupied metal d orbitals, and particularly to the favorable spatial arrangement of these d orbitals with respect to the carbonyl ligands. Bent-sandwich d2 complexes like [Zr(n5-C5H5)2(CO)2] exhibit comparable deshielding contributions from an occupied metal d orbital. For similar reasons, the 17O resonances for these piano-stool and bent-sandwich complexes are also predicted to be at unusually high frequencies, with low shift anisotropy. NMR shifts for the (n5-C5H5)-ligand atoms and the structures of the complexes are also discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020317
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Mechanism of solid-solid resolution of pantolactone (1996)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 795-800 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enantioselective solid-solid clathration of (S)-pantolactone (1) into (R,R)-trans-2,3-bis(diphenylhydroxymethyl)-1,4-dioxaspiro[4·4]nonane (2) and -[4·5]decane (3) was studied preparatively and mechanistically using atomic force microscopy (AFM) measurements and crystal packing data. Short-distance solid-to-solid sublimation mechanisms occur in both cases with initial formation of epitaxial floes along the b-axis in 2 and random craters in 3. The bulk control in the phase rebuilding stage is understood from the particular crystal packings. Bulk control was largely lost in the phase transformation stage when passivation of the surfaces occurred in both cases. The host lattices of 2 and 3 exhibit closed molecular double layers with all hydroxyl groups inside and lacking access for intercalation of 1. The reaction has to start at isolated surface defects. Once started, new doors for further entrance of guest molecules (S)-1 are opened in the double layer. For practical use, both the crystallographic difficulties and the passivation have to be overcome. A slurry technique involving addition of stoichiometric amounts of water to the solids provided useful conditions for the preparative resolution of (R/S)-1 or further racemates exhibiting passivation, whereas heating alone speeded up the resolution of 2-methylpiperazine with 2. © 1996 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Selektivitäten bei der Photolyse von Diphenylcyclobutenen (1978)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 3608-3623 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Selectivities in the Photolysis of Diphenylcyclobutenes[2 + 2]Photoaddition of diphenylacetylene (1) to electron-rich cycloalkenes 2, 5 yields cis-fused adducts, which in most cases are also prepared by treatment of stilbene adducts with NBS and pyridine. UV and fluorescence spectra as well as photolysis results are analyzed with respect to the feasibility of partial internal rotations of phenyl groups. For comparison, a series of related compounds 8-15 are included. The photoselectivities may be easily rationalized on the basis of quantum yields and product yields determined under various experimental conditions: if partial rotation is unhindered, α-cleavage, obtains; on the other hand, cyclization to labile 4a,4b-dihydrophenanthrenes occurs, if the helical conformation of the chromophor is sterically fixed. Only intermediate 19 undergoes a fast [4 + 4]cycloreversion to give the monocyclic diene 17 (indirect β-cleavage). In other cases related [4 + 4]photoreactions can be enforced by high intensities of polychromatic light. There are no indications for direct photochemical β-cleavages.
    Notes: Durch [2 + 2]-Photoaddition von Diphenylacetylen (1) an elektronenreiche Cycloalkene 2, 5 werden cis-verknüpfte Addukte erhalten, die größtenteils auch durch NBS- und Pyridinbehandlung von Stilbenaddukten gewonnen werden. Die UV- und Fluoreszenzspektren sowie Photolyseergebnisse werden im Hinblick auf interne partielle Rotationsmöglichkeiten der Phenylgruppen analysiert und mit einer Reihe weiterer 1,2-Diphenylcyclobuten-Derivate 8-15 verglichen. Die Photoselektivitäten können an Hand der Ausbeuteverhältnisse unter verschiedenen experimentellen Bedingungen und zusammen mit Quantenausbeutemessungen verstanden werden: Bei unbehinderter partieller Rotation tritt α-Spaltung, bei sterischer Fixierung der Schraubenkonformation des Chromophors Cyclisierung zu instabilen 4a,4b-Dihydrophenanthren-Derivaten ein. Nur beim Zwischenprodukt 19, wird die schnelle [4 + 4]-Cycloreversion zum monocyclischen Dien 17 (indirekte β-Spaltung) beobachtet. In anderen Fällen lassen sich entsprechende [4 + 4]-Reaktionen photochemisch erzwingen. Es gibt keine Anhaltspunkte für direkte photochemische β-Spaltungen.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19781111109
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The Photoelectron Spectrum of Dibenzo-p-quinodimethane (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 1949-1952 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lowest states of dibenzo-p-quinodimethane radical cation are 2B1u (7.95 eV); 2B2g (8.66 eV); [2B3g, 2Au, unresolved] (9.1 eV); [2B1u, 2B2g, unresolved] (10.7 eV). This confirms the assignment proposed by Koenig et al. [1] for the states of p-quinodimethane radical cation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590608
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    cis-Effekt bei photochemischen Cyclobutanspaltungen (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 3084-3110 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The cis-Effect in Photochemical Cleavages of CyclobutanesSelectivities in cleavage orientations on direct irradiation of cyclobutane derivatives are studied systematically at 20-30°C and -190°C with various examples. Phenyl and acrylic ester groups, in more or less sterically hindered environments, serve as chromophors. The cleavage reactions proceed via short-lived 1,4-diradicals. As a consequence of the two-step mechanism geometric isomerization of the cyclobutanes is observed and  -  as expected  -  there is no precisely reciprocal behaviour of fluorescence yields and photochemical quantum yields within series of related compounds. There is a clear preference for cleavage of the cyclobutane bond bearing i the chromophore and ii the substituent which sterically interacts most effectively with the chromophore (cis-effect). The application of the empirically supported effect to cyclovinylogous (retro-)Diels-Alder and [4 + 2 + 2]-reactions, e. g., is discussed. The syntheses and chemical or spectroscopic characterization (UV, fluorescence, NMR) of the compounds (phenylcyclobutanes, truxinic esters, dimers of muconic esters) investigated are described.
    Notes: Die Spaltungsorientierung von Cyclobutanderivaten nach direkter Lichtanregung wird an zahlreichen Beispielen bei 20-30°C und -190°C systematisch untersucht. Als Chromophore in sterisch mehr oder weniger stark behinderter Umgebung dienen Phenyl- und Acrylester-Gruppen. Die Spaltungsreaktionen verlaufen über kurzlebige 1,4-Diradikale. Als Folge des Zweistufenmechanismus werden geometrische Isomerisierungen der Cyclobutane beobachtet, und man erhält  -  wie erwartet  -  kein exakt reziprokes Verhalten von Fluoreszenzausbeuten und photochemischen Quantenausbeuten in Verbindungsreihen. Bevorzugt wird die Cyclobutan-Bindung gespalten, welche den Chromophor und die sterisch am stärksten auf diesen einwirkende Gruppe trägt (cis-Effekt). Die Anwendung des empirisch gesicherten Effekts, z. B. auf cyclovinyloge (Retro-)Diels-Alder- und [4 + 2 + 2]-Reaktionen wird diskutiert. Synthese und chemische sowie spektroskopische Charakterisierung (UV, Fluoreszenz, NMR) der untersuchten Verbindungen (Phenylcyclobutane, Truxinsäureester, Muconsäureester-Dimere) werden mitgeteilt.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771100914
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Abfallfreie Gas/Festkörper-Diazotierung mit Stickstoffdioxid und quantitative Triazensynthese ohne Flüssigphase (1997)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 339 (1997), S. 256-260 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Waste-Free Quantitative Gas/Solid Diazotation Using Nitrogen Dioxide and Triazene Synthesis, Both Avoiding Liquid PhasesSolid diazonium nitrates (2a-j) are quantitatively obtained by reaction of crystalline anilines (1a-j) with gaseous nitrogen dioxide. Solid diazonium salts react quantitatively with dimethylamine to give the triazenes (4a-j). Wastes that are typical for the previous syntheses of these compounds in solution are avoided. Atomic force microscopic (AFM) investigations indicate long-range molecular movements due to phase rebuilding. The features thus formed are related to the known crystal structures of the starting anilines. The diazotations run to completion, because, after accumulation of product molecules, phase transformation to give the product lattices leads to crystal disintegration and thus to formation of fresh surface over and over.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19973390145
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Neue Produkte durch Ringerweiterungen von festen 17-Hydroxy-20-ketosteroiden mit gasförmigem Chlorwasserstoff (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 686-689 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Products by Ring Expansions of Solid 17-Hydroxy-20-ketosteroids with Gaseous Hydrochloric AcidGaseous hydrogen chloride reacts directly with crystalline 17-hydroxy-20-ketosteroids like 17α-hydroxy-progesterones (1, 5, 6, 8) to give enlargement of ring D. In addition to the known acyloine rearrangement, new reaction types are observed which give rise to the products of substitutive rearrangement with elimination of water, 16β-Chloro-(3) and 16α-chloro-16β-methyl-17-oxo-D-homosteroids (7, 9) are formed stereoselectively. The drying agent magnesium sulfate may keep the reaction products solid. Mechanistic proof is provided spectroscopically (IR) and by the isolation of 17aβ-hydroxy-17aα-methyl-D-homoandrost-4-ene-3,17-dione (2) and its conversion to 16β-chloro-17aβ-methyl-D-homoandrost-4-ene-3,17-dione (3) with gaseous hydrogen chloride. The new reaction types do not occur in solution.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360808
    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...