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  • Chemistry  (8)
  • 1995-1999
  • 1990-1994  (8)
  • 1993  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Eigenschaften von Chalkogen-Chalkogen-Bindungen, XVII. Di-und Trisulfane mit sterisch anspruchsvollen Alkyl-Substituenten: Das erste trans1-Dialkyldisulfan (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1355-1359 
    Details
    ISSN: 0009-2940
    Keywords: Disulfanes ; Trisulfanes ; Bond conformations, S—S ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Properties of Chalcogen-Chalcogen Bonds, XVII[1]. - Di-and Trisulfanes with Sterically Congested Alkyl Substituents: The First trans1-DialkyldisulfaneBis[tris(trimethylsilyl)methyl]trisulfane (1) is obtained from tris(trimethylsilyl)methyllithium and sulfur with subsequent oxidation by oxygen or from tris(trimethylsily)methanethiol with sulfur dichloride. The solid trisulfane contains a transoid (helical) C—S-S—S-C backbone without severe distortion from steric strain. Desulfuration of the byproduct bis[tris(trimethylsilyl)methyl]tetrasulfane (2) with mercury provides 1, but further desulfuration of 1 to bis[tris(trimethylsilyl)1-methyl]disulfane (3) has not been achieved. 3 was isolated after oxidation of lithium tris(trimethylsilyl)methanethiolate with bromine. 3 contains a trans1-C—S-S—C moiety with an unusually long S—S bond (210-211 pm). The less crowded bis(triphenylmethyl)disulfane (4) contains a “normal” C—S-S—C moiety with anticlinal conformation (torsion angle - 110°).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260614
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  • 2
    Electronic Resource
    Electronic Resource
    Reaktionen an Silicium-Silicium-Bindungen, 3. Ein neuer Weg zur Knüpfung von Si - Ge-und Si - Sn-Bindungen: Hexachlordisilan-Spaltung von Organometallphosphanen und (Trichlorsilyl)phosphan-RecyclingHerrn Prof. Dr. Dr. h.c. U. Wannagat zum 70. Geburtstag gewidmet. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1115-1117 
    Details
    ISSN: 0009-2940
    Keywords: Germanes, silyl ; Stannanes, silyl ; Phosphanes, silyl ; Organometallphosphanes ; Recycling ; Si - Si bond ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions at Silicon-Silicon Bonds, 3[1]. - A New Path to Si - Ge and Si - Sn Bonds: Hexachlorodisilane Cleavage of Organometalphosphanes and (Trichlorosilyl)phosphane RecyclingTrimethyl(trichlorsilyl)germane and -stannane (4, 5) have been prepared through hexachlorodisilane cleavage by germyl-and stannylphosphanes R2PMMe3 (1, 2, R=i1-C3H7, t1-C4H9; M=Ge, Sn). The (trichlorosilyl)phosphane byproduct R2PSiCl3 (3) may be recycled by transmetalation and methylation steps to provide starting germylphosphane (MeGeCl3, 2 MeLi) and stannylphosphane (Me3SnCl, 3 MeLi).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260508
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  • 3
    Electronic Resource
    Electronic Resource
    Eigenschaften von Chalkogen - Chalkogen-Bindungen, XVII. - Di- und Trisulfane mit sterisch anspruchsvollen Alkyl-Substituenten: Das erste trans-Dialkyldisulfan (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1811-1811 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260809
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  • 4
    Electronic Resource
    Electronic Resource
    Multiblock poly(ether-ester-amide)s based on polyamide-6 and poly(ethylene glycol), 2Part 1: cf. ref.13. Effect of composition and soft-segment length on the structure of poly(ether-ester-amide)s as revealed by X-ray scattering (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 2267-2277 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Isotropic unannealed and annealed melt-pressed and quenched samples of segmented multiblock poly(ether-ester-amide)s based on polyamide-6 and poly(ethylene glycol)s (PEGs) of molecular weights 400 and 1000 with various hard/soft segment weight ratios were investigated. The effect of composition, segment length and annealing temperature on the crystal structure was studied by differential scanning calorimetry, wide-angle and small-angle X-ray scattering. In addition to the γ-phase, one of the unannealed samples having relatively long hard and soft segments exhibits a high amount of α-phase. This is assumed to be due to the high flexibility of the PEG segments, linking the polyamide blocks thus enhancing their mobility. The lack of hydrogen bonds between the PEG segments facilitates crystallization of the polyamide segments in the more perfect α-modification, which is the most pronounced in the above mentioned sample. Part of the α-phase transforms into the α-phase upon annealing in all copolymer samples studied, similarly to polyamide-6.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940811
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  • 5
    Electronic Resource
    Electronic Resource
    Use of AES to determine sputter-induced concentration profiles in Cu-Ni alloys (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 95-98 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The difference in escape depth of Auger electrons of different energies was used to determine sputter-induced concentration profiles in Cu-Ni alloys. Alloys with Cu/Ni concentrations of 70/30, 50/50 and 30/70 at.% were bombarded with 2 keV Ar+ ions. After equilibrium has been reached, an AES spectrum for the alloy was recorded using a 12-bit analogue-to-digital converter interfaced with a computer. Spectra for the pure elements, Cu and Ni, were recorded under identical conditions and were used to generate Auger spectra for the alloys that could be compared with the experimental data. The layer concentration values for which the best fit was obtained were used to construct a concentration profile. The results indicate a Cu-enriched first layer followed by a depleted zone. It is concluded that the bombardment of Cu-Ni alloys by 2 keV Ar+ ions leads to the segregation of copper and that AES can be used to determine sputter-induced profiles if the necessary experimental precautions are taken.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200114
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  • 6
    Electronic Resource
    Electronic Resource
    Neglected and hidden errors in the quantification of Auger electron spectroscopy (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 228-232 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Two types of errors made in the quantification of Auger electron spectroscopy (AES) are discussed in this paper. The first error is found in the discretization of the sample into layers parallel to the surface. It is shown that the conventional integral expression and the (discrete) summation differ in the calculated surface concentration value if the inelastic mean free path (IMFP) and interlayer distances vary from alloy to element. It is found that the disagreement may be as large as 50% for small IMFPs. The second error (or rather the absence of any indication of such errors) manifests itself in the four-way ratio of the intensities, i.e. IAIBelem/IBI Aelem, in the determination of the homogeneous surface concentration Xiφ. Any error made in the determination of Xiφ is hidden by the requirement that XAφ + XBφ = 1. It is proposed that the four-way ratio is split into two ratios, each yielding the respective concentration, and that the sum be used as an error indication.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200307
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  • 7
    Electronic Resource
    Electronic Resource
    2,3-Di-tert-butyl-1-telluradiphosphiran und verwandte Phosphor - Tellur-Heterocyclen (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 1083-1087 
    Details
    ISSN: 0044-2313
    Keywords: Phosphorus-tellurium heterocycles ; 2,3-di-tert-butyl-1-telluradiphosphirane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 2,3-Di-tert-butyl-1-telluradiphosphirane and related Phosphorus - Tellurium Heterocycles2,3-Di-tert-butyl-1-telluradiphosphirane was isolated in pure state by trap to trap condensation after reaction of 1,2-Di-tert-butyl-1,2-dichlorodiphosphane with sodium telluride in pentane suspension. The telluradiphosphirane and other P—Te heterocycles (t-BuP)nTem (n = 2, m = 1; n = 3, m = 1,2; n = 4, m = 1,2) are formed from 1,2-Di-tert-butyl-1,2-dichlorodiphosphane or tert-butyldichlorophosphane with bis(trimethylsilyl)telluride and from the reaction of tert-butylbis(trimethylsilyl)phosphane with elemental tellurium. The proposed structures of the P—Te heterocycles are based on 31P- and 125Te-n.m.r. and MS data
    Notes: 2,3-Di-tert-butyl-1-telluradiphosphiran läßt sich nach Umsetzung von 1,2-Di-tert-butyl-1,2-dichlordiphosphan mit Natriumtellurid in Pentan durch Umkondensation in 26% Ausbeute rein isolieren. Das Telluradiphosphiran entsteht neben anderen Phosphor - Tellur-Heterocyclen (t-BuP)nTem (n = 2, m = 1; n = 3, m = 1,2; n = 4, m = 1,2) bei den Umsetzungen von 1,2-Di-tert-butyl-1,2-dichlordiphosphan oder tert-Butyldichlorphosphan mit Bis(trimethylsilyl)tellurid sowie bei den Reaktionen von tert-Butylbis(trimethylsilyl)phosphan oder 1,2-Di-tert-butyl-1,2-dichlordiphosphan mit elementarem Tellur. Die Strukturvorschläge für die neuen Phosphor-Tellur-Heterocyclen basieren auf 31P- und 125Te-NMR- und Massenspektren.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190619
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  • 8
    Electronic Resource
    Electronic Resource
    Structure determination of a new saponin from the plant Alphitonia zizyphoides by NMR spectroscopy (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 472-480 
    Details
    ISSN: 0749-1581
    Keywords: Alphitonia zizyphoides ; Saponin ; 2D NMR ; INADEQUATE ; Molecular structure ; Computerized spectral analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-field NMR experiments, including the 2D INADEQUATE technique coupled with a computerized spectral analysis, were used to determine the full structure of a new saponin extracted from a plant (Alphitonia zizyphoides) found in the Samoan rain forests. The saponin, which shows significant pharmacological activity, consists of an aglycone framework of six rings (three saturated six-membered rings, two oxygen-containing five-membered rings and a five-membered carbon ring) to which are attached four sugar units and a six-carbon side-chain. The INADEQUATE experiment, which was carried out on 60 mg of sample, provided absolute confirmation of the assignments for 35 of the possible 53 C—C bonds from the 13C-13C connectivities.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260310511
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