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  • Articles  (40)
  • Computational Chemistry and Molecular Modeling  (27)
  • Physical Chemistry  (13)
  • 2020-2023
  • 1965-1969  (40)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 79-92 
    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 π-electron distributions, spin densities, and energies of the first triplets of the nucleotide bases, uracil, thymine, cytosine, adenine, and guanine, were investigated in various semiempirical approximations. Results are presented for calculations using the semiempirical form of the closed-shell SCF configuration interaction method, of the different orbitals for different spins (unrestricted Hartree-Fock) treatment, with and without spin projection, and of the Roothaan's open-shell procedure.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 571-580 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of methyl radicals to tetrafluoroethylene in the gas phase has been studied over the temperature range 80-180°C, using a material balance method. \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm CH}_{\rm 3} + {\rm C}_2 {\rm F}_{\rm 4} \to {\rm CH}_3 {\rm C}_2 {\rm F}_4 $$\end{document}Arrhenius parameters of 1011.95±0.23 (mole-1 cm3 sec-1) and 5.7 ± 0.4 (kcal/mole) have been measured for the addition reaction.Electrophilic reagents such as O or CF3 appear to react almost equally readily with ethylene and tetrafluoroethylene but methyl radicals add much more rapidly to tetrafluoroethylene than to ethylene, the difference in reactivity being principally due to an activation energy difference of ∼2 kcal/mole.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 373-376 
    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
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 913-930 
    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: A theory for handling non-orthogonal radial orbitals of two shells of atomic electrons based on the mathematical apparatus of irreducible tensor operators is presented. The general expressions for one- and two-electron operator matrix elements are given.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 1013-1025 
    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: All-electron SCF-LCAO-MO computations for diazomethane, ketene and allene are presented. The basis functions are contracted Gaussian orbitals. Theoretical results are discussed and related to available experimental data.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 149-167 
    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 general formulas which are convenient for cluster analysis of a configuration interaction wave function are presented. These formulas are then used for cluster analysis of the “complete” configuration interaction wave functions of the π-electronic models of benzene and butadiene obtained with a semiempirical method of the Pariser-Parr-Pople type using three different parameterizations. For butadiene the calculations are carried out with Hückel, Hartree-Fock, and Brueckner molecular orbitals. The results clearly indicate that Sinanoǧlu's statement [1, 2], concerning the relative unimportance of the linked parts of the tetraexcited state coefficients in the ci expansion, is justified for these delocalized systems.
    Additional Material: 5 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 339-351 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following Arrhenius parameters have been determined for the hydrogen-abstraction reactions: R + (CH3)4Si → RH + (CH3)3SiCH3 TextRTemp. (°K)E (kcal/mole)Log A (mole-1 cc sec-1)Log k(400°K) (mole-1 cc sec-1)CF3330-4337.23 ± 0.0911.90 ± 0.057.95CH3396-47610.23 ± 0.3611.55 ± 0.185.68CD3396-49610.36 ± 0.1211.84 ± 0.066.20C2H5423-52211.40 ± 0.4811.88 ± 0.225.68The activation energies are in keeping with the strengths of the bonds formed during the reaction. By comparison with the activation energies for the analogous reactions of neopentane it is estimated that D((CH3)3SiCH2—H) ≃ 97 kcal/mole.The A factors for the above series of reactions fall within the range predicted by transition-state theory for this type of process and the validity of previous results of Kerr, Slater, and Young is seriously in doubt.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 1 (1969), S. 371-380 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Arrhenius parameters have been determined for the hydrogen-abstraction reactions: R + SiHCl3 + RH + SiCl3 TextRTemp (°K)E(kcal/mole)Log A(mole-1 cc sec-1)Log k(400°K) (mole-1 cc sec-1)CF3323-4615.98 ± 0.0611.77 ± 0.038.50CH3333-4434.30 ± 0.0810.83 ± 0.044.48C2H5314-4135.32 ± 0.0711.54 ± 0.048.63The trend in activation energies ECH3 〈 EC2H5 〈 ECF3 is interpreted as indicating a polar effect in the reaction of CF3 with SiHCl3 and the similar reactivities of all three radicals appear to be due to the high exothermicity of the reactions.The A Factors for the reactions are normal for hydrogen abstraction reactions of free radicals. The previous results of Kerr, Slater, and Young for CH3 abstracting an H atom from SiHCl3 have been amended.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 2 (1968), S. 521-530 
    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
    Description / Table of Contents: On a observé que certains substituants introduits sur un système acénique peuvent changer le lieu de la fixation de l'oxygène au cours de la photooxydation. Ce fait ne peut ětre interprété en calculant les énergies de paralocalisation. L'hypothèse d'un complexe intermédiaire correspondant à une extension du systeme délocalisé permet au contraire de rendre trés bien compte des résultats expérimentaux.
    Abstract: Es wurde bemerkt, dass gewisse Substituenten, die in Acenderivaten eingeführt sind, den Anheftungsplatz des Sauerstoffs während der Photooxydation verändern können. Dieses Phänomen kann nicht mit einer Berechnung der Paralokalisierungsenergien erklärt werden. Wenn aber ein intermediürer Komplex eingeführt wird, was einer Erweiterung der delokalisierten Bindung entspricht, ist es möglich eine befriedigende Erklärung der experimentellen Tatsachen zu geben.
    Notes: It has been observed that some substituents introduced in acenic derivatives are able to change the site of the fixation of oxygen during photooxidation. It is not possible to interpret this phenomenon by calculating the paralocalization energies. However, if an intermediate complex is introduced, which corresponds to an extension of the delocalized bond, a satisfactory explanation of the experimental results is possible.
    Additional Material: 3 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 3 (1969), S. 969-981 
    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: A review is given of the current status of our work on electron transport properties and Fermi surfaces in simple metals. A simple classical model is proposed to extend existing theory to account for the effects of electron-impurity interactions on the behavior of magnetoacoustic absorption and the size and shape of the Fermi surface in the alkali metal potassium. The theoretical prediction is compared with measurements of the magnetoacoustic absorptionand Fermi surface diameters in potassium crystals of different impurity levels. An attempt is made to explain, on the basis of the theory of electron-impurity interactions, the decrease by 9% in the Fermi diameter and the departure by 53% in the phase factors of the impure potassium crystal. The results are compared with observations on a zone refined potassium crystal which satisfies the nearly-free-electron model.
    Additional Material: 3 Ill.
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