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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 69 (1986), S. 107-117 
    ISSN: 1432-2234
    Keywords: Graph theory ; Acyclic polynomial, coefficients of ; structure count ; Sachs graphs ; Kekulé structures ; Dewar structures ; Biradicals ; Radical-cations ; Canonical structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A generalized approach to the structure count of n-radical-m-cation systems based on the properties of the acyclic polynomial is presented. The mathematical proof for the expression relating the structure count to the coefficients of the acyclic polynomial is given. The connection between the structure count of biradical structures and the number of Dewar structures is discussed and tested on some examples.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemie der Cumarine. - Nucleophile Substitutionen an 4-Chlor-3-nitrocumarin mit harten und weichen NucleophilenUmsetzungen von 4-Chlor-3-nitrocumarin mit verschiedenen Nucleophilen ergaben zahlreiche neue substituierte Cumarine. Harte Nucleophile und solche im Übergangsbereich zu den weichen substituieren ausschließlich das Chlor in Position 4, während weiche Nucleophile (mit Ausnahme von Iodid) die Nitrogruppe in Position 3 der Titelverbindung ersetzen. Dieses Ergebnis wird mit Hilfe der Theorie von den harten und weichen Säuren/Basen diskutiert.
    Notes: Reactions of 4-chloro-3-nitrocoumarin with a variety of nucleophiles produced a number of novel substituted coumarins. Hard and borderline nucleophiles exclusively substitute chlorine in position 4, while soft nucleophiles substitute the nitro group in position 3 (except for iodide) of the title compound. This result of the nucleophilic substitution of 4-chloro-3-nitrocoumarin is rationalized in terms of the HSAB model.
    Type of Medium: Electronic Resource
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