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  • Biochemistry  (2)
  • Wiley-Blackwell  (2)
  • American Physical Society
  • 1980-1984  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Evaluation of MINDO/3 calculated structures. II. Branching errors in alkanes and cycloalkanesFor Part I see ref. 1. (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 233-239 
    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: MINDO/3 calculations have been carried out for a series of branched chain alkanes in order to assess effects of branching on calculated geometries and heats of formation (ΔHf). With vicinal branching, MINDO/3 calculates the central C—C bond to be too long. Bond angles are also found to be distorted. Errors in calculated heats of formation are large when geminal branching is present and significant with vicinal branching. Branching error corrections for ΔHf have been derived and applied to a separate series of branched acyclic and cyclic compounds. For the test sample, application of the branching error corrections gave calculated structures of acyclic branched hydrocarbons with heats of formation having an average absolute error of 1.3 kcal/mole rather than 17.3 kcal/mole before correction. Cyclic branched hydrocarbons are shown to be less well corrected. Calculations of heats of reaction have also been carried out for some isomerization and cyclization reactions using the MINDO/3 and MNDO methods. It is clear from the comparisons that MNDO calculations give less severe errors for highly branched compounds but the errors are still substantial. For prediction of heats of reaction, the error-corrected calculations are shown to be superior to the “raw” calculations obtained by MINDO/3 or MNDO.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540010304
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  • 2
    Electronic Resource
    Electronic Resource
    Evaluation of MINDO/3 calculated structures. III. Saturated acyclic compounds with chlorine, nitrogen, oxygen, or sulfurFor Part II see ref. 1. (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 3 (1982), S. 229-233 
    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: Fifty-one structures have been calculated by the MINDO/3 method to evaluate the errors introduced by branching and by the presence of the heteroatom. The structures are evaluated by comparisons which reveal that the calculated ΔHf values reflect a bias because of the presence of the heteroatom. With two carbons or more in a chain attached to a heteroatom group, a linear relationship exists which makes possible the calculation of reasonably accurate ΔHf values for unbranched alcohols, primary or secondary amines, ethers, thioethers, thiols, and alkyl chlorides. Branching errors do not seem to be linearly related among the systems. Some errors in calculations of geometries are also discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540030215
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