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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical study of the thermal unimolecular rearrangement of fluoroethylidenes (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 363-377 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal unimolecular isomerization of fluoroethylidenes to the corresponding fluoroethylenes has been studied by the MNDO method. It has been shown that fluorine substitution on the carbene carbon increases the activation energy in comparison with the ethylidene rearrangement. To understand the reason for this increase in the activation energy, the charge-transfer effects have been analyzed. Fluorine substitution at other positions does not significantly affect the activation energies. The thermodynamic parameters for the reaction have been evaluated, using vibrational and rotational spectral data calculated in this work. RRKM calculations have been performed and high-pressure Arrhenius parameters calculated. Hydrogen-deuterium kinetic isotope effects indicate that the reaction rates are altered considerably on isotopic substitution, and the change in reaction rates depends upon the position of deuterium substitution, as well as on the number of hydrogens replaced by deuterium atoms. © 1992 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440305
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    C3H4: Theoretical study of structures and stabilities of isomers (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 58 (1996), S. 389-398 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The various isomers including stable structures, carbenes, and diradicals on the C3H4 surface have been investigated. The two carbenes propenylidene and cyclopropylidene have been found to have singlet ground states. Vinylmethylene is predicted to have a triplet ground state with a planar diradical type of structure. The syn and anti forms of this state are degenerate. This is in agreement with the observation of two triplet states in the electron spin resonance (ESR) spectra. The π electrons are found to be delocalized over the three carbons. The singlet diradical structures are found to be more stable than the carbene structures, which retain the CH2 (DOUBLE BOND) CH allylic structures. The orbital compositions of the frontier orbitals of all systems have been determined to examine the nature of these orbitals. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Unimolecular rearrangements of ethylnitrene: An exploratory theoretical study (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 1211-1216 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The products of the rearrangement of ethylnitrene are ethylideneimine via a 1,2 hydrogen shift, N-methyl methyleneimine via a 1,2 methyl shift, and the corresponding aziridine by cyclization. The three reactions have been studied by the semiempirical MNDO method. The charge transfer effects have been investigated. Theoretically calculated vibrational frequencies and kinetic properties have been used in calculating macroscopic thermodynamic and kinetic properties. The entropies of activation, the high pressure rate constants, k∞, and the high pressure Arrhenius parameters, A∞ and E∞, have been computed. The kinetic isotope effects have also been studied.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540121007
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    Paper (German National Licenses)
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