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  • 1
    Electronic Resource
    Electronic Resource
    The mass spectra of some pyrazole compounds (1970)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1970), S. 1549-1559 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of ten pyrazole compounds have been determined. Fragmentation schemes have been derived by means of the metastable defocusing method. The predominant process is cleavage of the nitrogen-nitrogen bond resulting in expulsion of HCN. The process second in prominence is the loss of a nitrogen molecule after initial removal of a hydrogen radical or a substituent, giving the species [C3H2R]+, probably a cyclopropenyl ion. In general, the fragmentation pattern is strongly influenced by the substituent.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210031213
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  • 2
    Electronic Resource
    Electronic Resource
    Preference factors and isotope effects in the loss of H. (D.) and HCN (DCN) from deuterated pyrazoles upon electron-impact (1971)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1971), S. 1101-1105 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of deuterated pyrazoles show that loss of H. and of HCN from the molecular ion occurs with a very high specificity from the 3(5)-position. For the two processes isotope effects and preference factors have been determined. Metastable ion decompositions involving the loss of HCN from the [M - H] -fragment indicate that the identity of the hydrogen atoms in this fragment is lost to a large extent.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210050910
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Fragmentation behaviour and ring expansion of 1-methylimidazole and 1-methylpyrazole upon electron-impact (1973)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 7 (1973), S. 1165-1172 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relative losses of unlabelled vs. labelled HCN from the [M]+· and [M - 1]+ ions of a number of specifically labelled 1-methylimidazoles (I) and 1-methylpyrazoles (II) have been determined. Hydrogen randomisation in the molecular ions prior to fragmentation is insignificant. Expulsion of HCN follows two distinct pathways: elimination involving positions 2 and 3 (predominant in I) and elimination involving the methyl group and the nitrogen atom at position 1 (predominant in II). The molecular ions eject H· from the methyl groups to a high degree of specificity. In both cases some contribution by position 5 is observed. The resultant [M - 1]+ ions exhibit extensive, but incomplete hydrogen randomisation. Loss of HCN from these ions is consistent with intermediacy of ring-expanded ions, but notably in II a proportion of the HCN is generated from the group. A mechanism for this observation is presented.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210071005
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  • 4
    Electronic Resource
    Electronic Resource
    The formation and structure of radical cations (1977)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1977), S. 196-199 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ions generated from a number of different presursors have been studied by high kinetie energy ion - molecule reations. It has been shown that at least four distinct stable species oeeur, of which acetonitrile and methyl isoeyanide retain their original structure. With imidazole or pyrazole as precursors, a mixture of open thain radical cations, not identical to the above species and probably interconvertible via the 1H-azirine radocal cation, is formed. From butrynitrile, pyrrole, crotonitrile, allyl interconvertible via the and cyanocyopropane a fourth species, probably the vinylidenimine ion, is formed.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210120403
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  • 5
    Electronic Resource
    Electronic Resource
    The structure of [C3H4N2]+· and [C5H5N2]+ ions formed from vinylimidazoles, studied by collisionally activated dissociation mass spectrometry (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1984), S. 16-22 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of the three isomeric vinylimidazoles have been compared and the structures of the fragment ions [C3H4N2]+· and [C5H5N2]+ have been investigated by collisionally activated dissociation mass spectrometry. The greater part of the non-decomposing ions m/z 68 from 2-vinylimidazole and from 2-imidazolecarboxylic acid methyl ester, and a minor part of this ion formed from the free acid, all have the same structure: the imidazole ring system, with hydrogens at both nitrogen atoms but none at C(2). An analogous structure, with an ethyl group at C(2), is proposed for the m/z 93 ion from 2-vinylimidazole.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210190105
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  • 6
    Electronic Resource
    Electronic Resource
    Loss of HCN and H⋅ from the molecular ion of imidazole (1972)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1972), S. 1363-1368 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behaviour of a number of deuterated imidazoles upon electron-impact has been studied. Loss of H⋅ from the molecular ion occurs specifically at the 4(5)-position. Loss of HCN is less specific, the order being 2 〉 4(5) ≫ 1.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210061211
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