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  • 1
    Electronic Resource
    Electronic Resource
    Chiral discrimination in nonracemic mixtures of methanephosphonic acid, N,N′-bis(1-phenylethyl)diamides (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 1-4 
    Details
    ISSN: 0899-0042
    Keywords: methanephosphonic acid dichloride ; N,N′-bis(1-phenylethyl)diamidomethylphosphonate ; chiral discrimination on self-association ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomeric (S,S)- and (R,R)-bis(1-phenylethyl)diamidomethylphosphonates, the phosphorus atom being prochiral, have been synthesized, starting from the methanephosphonic acid dichloride and corresponding chiral amines. The splitting observed in the 31P-NMR spectra of their nonracemic mixtures may be accounted for the self-discrimination of chiral species. This effect can be very useful for enantiomeric analysis of amines based on coupling reactions with methanephosphonic acid dichloride. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060103
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  • 2
    Electronic Resource
    Electronic Resource
    NMR investigations of the enantiomeric excess effects in solutions with weak intermolecular association (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 326-330 
    Details
    ISSN: 0899-0042
    Keywords: enantioselectivity ; NMR ; self-association ; achiral solvents ; dimerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The main features of statistically controlled associate diasteromerism (SCAD) in solution as measured by nuclear magnetic resonance (NMR) are discussed. In an achiral solvent, (R)- and (S)-enantiomers can demonstrate distinct NMR signals, with the intensity ratio equal to the concentration ratio. The previous theory of SCADA (anisochronism of nuclear magnetic moments caused by SCAD) is supplemented by treatment of enantiomeric excess phenomena in relation with the hypothesis that a sample consists totally of short-living diastereomeric dimers which are involved in fast (on the NMR time scale) exchange by enantiomers. Thermodynamic parameters of SCAD as well as limits for enantioselectivity phenomena are estimated. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070503
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    NMR study of polycrystalline azoles (1991)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 4 (1991), S. 271-276 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polycrystalline pyrazole, imidazole and benzotriazole were investigated by 1H and 2H NMR spectroscopy. In addition to the usual broad line of the 1H NMR signal due to the dipole-dipole interaction, a significantly narrowed component (δν = 1-2 kHz) of a complex triplet structure was detected in all three compounds. To interpret this observation, a mechanism with virtually complete averaging of the dipole-dipole interaction for a small part of the sample protons is suggested. The mechanism is based on proton interaction with the unpaired electron of a short-lived radical of the type Az· or (H-Az·-H).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610040503
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    Paper (German National Licenses)
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