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  • 1
    Electronic Resource
    Electronic Resource
    MNDOC-CI calculations for organic photoreactions. I. The α-cleavage reaction of carbonyl compounds (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 81-88 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: MNDOC-CI results are reported for the photochemical α-cleavage reaction of carbonyl compounds. Potential energy surfaces for some excited singlet and triplet states and cross-sections along the bitopic reaction path show that the activation energy of the α-cleavage reaction is determined by the relative energetic position of the lowest two triplet states. The reactivity of aliphatic ketones depends only on the degree of branching at the α-carbon, because the triplet barrier is due to an (avoided) crossing of two surfaces corresponding to an nπ* and ππ* excitation respectively, which correlates with the stability of the leaving alkyl radical. For conjugated carbonyl compounds, on the other hand, the position of the crossing point is independent of the 3nπ* excitation energy, but if the 3ππ* surface is below the 3nπ* surface all the way along the reaction coordinate, the reaction is determined by the barrier on the 3ππ* surface and any additional stabilization of the 3ππ* state increases the barrier.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030204
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  • 2
    Electronic Resource
    Electronic Resource
    Konfigurationsabhängigkeit der 13C-13C-Kopplungskonstanten in 1,2-disubstituierten Cyclopropanen (1979)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1979 (1979), S. 1960-1964 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Configurational Dependence of 13C-13C Coupling Constants in 1,2-Disubstituted CyclopropanesThe three [2-13C]mono- and [2-13C]dibromo(methyl)cyclopropanes 2-4 as well as [1-13C]-methylcyclopropane (1) were synthesized and the 13C-13C coupling constants were determined. For the coupling between the substituted carbon atoms 1JC,C (trans) 〉 1JC,C (cis) was found. Calculations showed that 1JC,C depends on the dihedral angle between the substituents, the effect being more pronounced for polar substituents than for methyl groups.
    Notes: Die drei [2-13C]Mono- und [2-13C]Dibrom(methyl)cyclopropane 2-4 sowie [1-13C]Methylcyclo-propan (1) wurden synthetisiert und die 13C-13C-Kopplungskonstanten bestimmt. Für die Kopplung zwischen den substituierten Kohlenstoffatomen gilt: 1JC,C (trans) 〉 1JC,C (cis). Berechnungen der Kopplungskonstanten zeigen, daß 1JC,C vom Diederwinkel Φ zwischen den Substituenten abhängt, wobei der Effekt für polare Substituenten größer ist als für Methylgruppen.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197919791205
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