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  • Organic Chemistry  (2)
  • 1D-INADEQUATE  (1)
  • 1
    Digitale Medien
    Digitale Medien
    A Comparative 1H- and 13C-NMR Study of the Dianion and Dication of Biphenylene (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 955-961 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Biphenylene dianion has been prepared by Li reduction of the parent hydrocarbon. It is stable below -30° and was characterized by its 1H- and 13C-NMR spectra. A comparison of these data with those of the dication indicates the existence of ion pairs in the dianion case which are responsible for a different charge distribution. The diamagnetic ring currents of both ions, however, are of comparable magnitude, and both are more diatropic than the parent hydrocarbon. Predictions of the π-charge-density effect on 1H chemical shifts are improved by calculations that use the linear and quadratic electric-field effect equation instead of the simple Spiesecke-Schneider relation.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19860690502
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  • 2
    Digitale Medien
    Digitale Medien
    Solvation of indenyllithium and indenylpotassium studied by 13C NMR spectroscopy (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 9-12 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Polarization of the π-electron systems of indenyllithium (In -Li+) and indenylpotassium (In -K+), which is generally indicative of the degree and tightness of contact ion pairing, was investigated by 13C NMR spectroscopy. The effect of changing solvent is about two thirds as great for In -K+ as for In -Li+. The indenyl anion is more strongly polarized with Li+/dimethyl sulfoxide than with Li+/ammonia, whereas the reverse is observed for In -K+. Complexation of In -K+ in tetrahydrofuran (THF) by cryptand(2,2,2) results in a π-electron distribution identical with that of In -Li+ in hexamethylphosphoramide, indicative of solvent- or agent-separated ion pairs or free ions. Small but significant cation-anion interactions are observed for In -K+ in hexamethylphosphoramide and for In -N+Me4 in THF.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610030103
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  • 3
    Digitale Medien
    Digitale Medien
    Natural abundance one-bond 13C—13C coupling constants and unambiguous assignments of 13C NMR chemical shifts of dithieno[b,d]pyridines; a multivariate data analysis (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 33-41 
    Details
    ISSN: 0749-1581
    Schlagwort(e): Dithieno[b,d]pyridines ; 13C NMR ; 1D-INADEQUATE ; Multivariate data analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The one-bond 13C—13C coupling constants (1JCC) in all nine possible dithieno[b,d]pyridines were measured at natural isotope abundance by using the INADEQUATE pulse sequence technique. The unambiguous assignments of the 13C NMR shifts of these compounds are also reported. Assignments are based on proton decoupled 13C spectra, heteronuclear correlation spectra (HETCOR) and 1D-INADEQUATE 13C NMR spectroscopy. The effect of the fusion pattern and the influence of the heteroatoms in the ring skeleton on the NMR parameters are discussed. By a multivariate principal components data analysis, it was shown that the magnitude of 1J(CC) of the pyridine subunit could be satisfactorily predicted from shift data, the azomethine C—H coupling constant and MNDO bond orders. The last parameter gave only a minor contribution to the coupling variability.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260280108
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