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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 893-904 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A method has been developed which uses a rapid connectivity-based calculation to give a reasonable approximation of CNDO σ and π charges for most carbons in saturated and unsaturated hydrocarbons. In this calculation an appropriately parameterized Del Re method is used to calculate the σ charges, and if the molecule is unsaturated, these charges are used to modify the diagonal elements in a Hückel matrix, reducing the normally exaggerated π charges. The CNDO charges are obtained from “single point” calculations, using optimized geometries derived from molecular mechanics. The Del Re/Hückel method is most reliable where steric and hyperconjugative effects are absent.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 990-996 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A rapid method for estimating CNDO charges in large data bases using a reparameterized Del Re method has been described previously. In this article the method is extended to saturated compounds containing B, N, O, F, Si, P, S, and Cl. Good results are obtained by forcing the Del Re δo parameter for each element to be linearly related to its Pauling electronegativity, but with the slopes and intercepts being different for second- and third-row elements. With a test set of 17 compounds and 71 atoms, the CNDO charge was reproduced with an average deviation of ±0.03. The largest deviations, up to ±0.2, were observed for carbons having multiple F or Cl substituents and for sterically hindered atoms. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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