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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1980), S. 92-100 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the electron impact mass spectra of azomethines derived from various substituted aromatic aldehydes and diarninodicyanoethene the superposition of two ortho effects concurring with the azomethine group is apparent: one involving the amino group of the diaminodicyanoethene part accounts for the cyclization to [C5H3N4]+ ions and the other involving ortho substituents of the benzylidene part which can interact with the azomethine moiety is responsible for specific fragment ions, suppressing the typical fragmentations of azomethines. The ortho effect was studied for the o-nitro derivative by labelling experiments, analysis of metastable transitions and collisional activation comparing model ions, demonstrating that the specific [M-H2O]+· and [C7H5NO2]+· ions are the result of cyclization processes.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 10 (1975), S. 97-115 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron-impact and field ionisation spectra of nineteen di- and tetracyanopyrazines are presented. The use of high resolution mass measurement and metastable analysis allows the proposal of some general fragmentation mechanisms. The 5,6-disubstituted (alkyl or arene) 2,3-dicyanopyrazines examined show, apart from a less important loss of the nitrile and dicyano groups, fragmentation of the heterocyclic system directed by the nitrogen atoms. In contrast, anellation in the 5,6-position, leads only to loss of the nitrile and dicyano groups being observed. These general fragmentation mechanisms are also observed for the tetracyanopyrazines examined. A comparison of di- and tetracyanobenzene with five ring heterocycles containing four cyano groups shows that fragmentation of nitrile groups is greatly dependent upon the aromaticity of the cyclic system.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1978), S. 371-378 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The electron impact mass spectra of azomethines formed from diaminodicyanoethene are characterized by the formation of cyclic products involving the amino group of the diaminodicyanoethene and the azomethine group. The ions are shown to have imidazole structures by analysis of the metastable transitions and collisional activation spectra of both positive and negative ions and the kinetic energy release and by comparing these with authentic model ions. The source of the HCN lost, which is a characteristic process, was shown by deuterium labelling to be diaminocyanomethane residue and not the azomethine group, in contrast to other anils.
    Notes: Die elektronenstoßinduzierten Zerfälle Schiffscher Basen des DMD (Diaminomaleinsäuredinitril) werden durch Cyclisierungsreaktionen der Aminogruppe des DMD-Restes mit der Azomethingruppierung beherrscht. Die innerhalb der Zerfallsprozesse gebildeten Imidazolsysteme werden durch MI- und CA- Spektren unter positiven und negativen Ionisierungsbedingungen sowie durch Vergleich des kinetic energy release unter Hinzuziehung von Modellionen bewiesen. Deuterierungsexperimente zeigen, daß die für Anile charakteristische HCN-Eliminierung nicht unter Angriff der Azomethingruppierung sondern ausschließlich über den DMD- Rest ablaüft.
    Additional Material: 5 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1978), S. 636-641 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The negative ion mass spectra of cyano substituted heterocyclic compounds show specific fragmentation pathways which are of analytical importance for the distinction between isomeric compounds. All the compounds examined fragment directly to give or ions. The ion structures involved were determined by the analysis of the metastable transitions and collisional activation spectra. The fragmentations of tetracyano substituted heterocyclic compounds are explained by rearrangement processes of the molecular anions.
    Notes: Die EA-Spektren cyansubstituierter Heterocyclen zeigen spezifische Fragmentierungen, die eine massenspektrometrische Unterscheidung isomerer Systeme gestatten. Die Strukturen der aus den Molekülanionen bzw. [(M - H)]- -Ionen direkt gebildeten -Ionen werden durch Vergleich der MI- bzw. CA-spektren verschiedener Vorläuferionen untersucht. Das Fragmentierungsverhalten von Tetracyan-substituierten Heterocyclen setzt Umlagerungen der Molekülanionen voraus.
    Additional Material: 2 Ill.
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