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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 82 (1970), S. 187-202 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aktiver Stickstoff entsteht durch elektrische Entladung in strömendem Stickstoff und gibt sich durch das charakteristische gelbe Nachleuchten zu erkennen. Zum quantitativen Nachweis eignet sich z. B. die Umsetzung mit Stickstoffoxid („Gasphasen-Titration“). Der aktive Stickstoff setzt sich mit zahlreichen Elementen sowie anorganischen und organischen Verbindungen um. Seine wichtigsten Reaktionen sind auf Stickstoffatome zurückzuführen; daneben sind aber auch elektronisch angeregte Moleküle beteiligt.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four analogs of the acetylenic alkaloid, histrionicotoxin (C19H25NO) and the allenic alkaloid, isodihydrohistrionicotoxin have been isolated from extracts of skins of the arrow poison frog, Dendrobates histrionicus and characterized as neodihydrohistrionicotoxin, tetrahydrohistrionicotoxin, isotetrahydrohistrionicotoxin and octahydrohistrionicotoxin. These spiropiperidine (8-hydroxy-1-azaspiro[5.5]undecane) alkaloids differ only in the degree of unsaturation in the five carbon atoms (position 2) and four carbon atoms (position 7) side chains. A fifth compound, HTX-D, corresponds in empirical formula to a tetrahydrohistrionicotoxin with a 7-(cis-1-butenyl-3-ynyl) side chain, but the major mass spectral fragmentation with loss of C2H5O is not characteristic of the histrionicotoxins. Reduction of histrionicotoxin with hydrogen and Lindlar catalyst affords an isomeric dihydrohistrionicotoxin with the terminal acetylene of the five carbon atoms side chain reduced, tetrahydrohistrionicotoxin and hexahydrohistrionicotoxins, while reduction with hydrogen and palladium on charcoal affords dodecahydrohistrionicotoxin which is readily methylated to the tertiary amine by methyl iodide.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 9 (1971), S. 1117-1138 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study was made of polyimides based on pyrazinetetracarboxylic dianhydride (PTDA) plus heterocyclic diamines different from the one previously reported by Hirsch. It was postulated that thermal properties might be improved if the diamine portion did not contain the N-N linkage. The results indicate that these heterocyclic-based polyimides are in fact of lower thermal stability and of less molecular weight buildup than their corresponding polypyromellitimides. Thermal failure, outlined by their TGA curves, is shown not to be due to an inherent lack of stability for such polymers, but rather, to synthesis problems arising from both the anhydride and amine precursors. The synthetic problems are twofold: (1) the heterocyclic diamines used in this study display low reactivity; (2) pyrazinecarboxylic acids readily decarboxylate. These conclusions were drawn from a correlation of the relative basicity values of the diamines of consideration and from study of a series of model compounds prepared from an appropriate amine or diamine with PDTA, pyrazinedicarboxylic anhydride, phthalic anhydride, or pyromellitic dianhydride. An accumulation of infrared and mass spectra data for these models relate that the proposed pyrazine polyimides are not of complete polyimide structure, but rather resemble recurring amide-imide units.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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