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  • 1
    Electronic Resource
    Electronic Resource
    Electron spin resonance study of some polycyclic nitrogen heterocyclic radical anions (1984)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 22 (1984), S. 521-526 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In dimethylformamide the ESR spectra of the radical anions of dibenzo[f,h]quinoxaline and dibenzo[a,c]phenazine both exhibit line broadening due to slow molecular tumbling over a wide temperature range. Similar effects are also observed in the spectra of the radical anions of quinoxaline and phenazine. The ESR spectra of the radical anions of dibenzo[f,h]quinoxaline and dibenzo[a,c]phenazine have been interpreted by computer reconstruction and the hyperfine splitting constants assigned with the aid of Hückel unpaired electron density calculations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270220810
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of crown ethers on cation migration processes. Part 7.1 The 2-pivaloyl-1,4-benzoquinone radical anion (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 953-958 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; Cation migration ; Line-width variation ; 2-Pivaloyl-1,4-benzoquinone ; Radical anion ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2-pivaloyl-1,4-benzoquinone radical anion has been prepared by alkali metal reduction in tetrahydrofuran in the presence of dibenzo-18-crown-6, 15-crown-5, or 12-crown-4, and its ESR spectrum in each system has been recorded over a range of temperatures. Line-width variation in the ESR spectrum is observed in some systems. This line-width variation has been attributed to cation migration between sites adjacent to the non-equivalent carbonyl groups rather than to restricted rotation of the pivaloyl group. In some systems, however, the rate of migration is too fast and in others too slow, compared with the time-scale of the ESR experiment, for line-width variation to be observed. The influence of each crown ether upon the rate of cation migration has been found to depend upon the size of the crown ether ‘cavity’ compared with the size of the alkali metal counter-ion.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260271010
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  • 3
    Electronic Resource
    Electronic Resource
    Spin-trapping artifacts on addition of polyacrylonitrile and poly(methyl methacrylate) to dimethyl sulphoxide (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 626-631 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; Spin Trapping ; Occluded radicals ; Polyacrylonitrile ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ESR spectrum is observed when a sample of polyacrylonitrile powder is dissolved in a dimethyl sulphoxide solution of nitrosobenzene at room temperature. However, the spectrum is not associated with the trapping of occluded radicals from within the polymer latex, but with the hydrogen atom adduct. [Similarly, when an aqueous emulsion of poly(methyl methacrylate) is added in place of the polyacrylonitrile powder the spectrum of the hydrogen atom adduct is again observed.] Experiments in dimethyl-d6 sulphoxide indicate that the hydrogen atom does not originate from the solvent. At higher temperatures (383 K) the spectrum of a mixture of the hydrogen atom and methyl radical adducts is observed. Experiments in dimethyl-d6 sulphoxide show that the latter radical originates from the solvent.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300709
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