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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 407-410 
    ISSN: 0894-3230
    Keywords: gas-phase thermolysis ; N-methyl-N-phenyl-tert-butylsulfenamide ; morpholinyl-tert-butylsulfenamide ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Methyl-N-phenyl-tert-butylsulfenamide (MPSA) and morpholinyl-tert-butylsulfenamide (MOSA) were thermolyzed in a stirred-flow reactor at temperatures of 340-390 °C and pressures of 7-13 Torr, using toluene as carrier gas, at residence times of 0.3-1.3 s. Isobutene was formed in 99% yield through first-order reactions having the following Arrhenius parameters (A,s-1, Ea, kJ mol-1): MPSA, log A  =  12.41 ± 0.02, Ea  =  158.8 ± 0.2; MOSA, log A  =  12.91 ± 0.22, Ea  =  159 ± 3. It is proposed that the elimination of isobutene takes place by unimolecular reaction mechanisms involving polar, four-center cyclic transition states, forming S-unsubstituted thiohydroxylamines as co-products. Thermochemical parameters, estimated by semiempirical AM1 calculations, are reported for the latter and for the parent molecules. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 49-54 
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---Various diallyl- and allylpropargylamines were pyrolyzed in a stirred-flow reactor at temperatures in the range of 330-500°C, pressures of 8-16 Torr and residence times of 0·4-2·4 s using toluene as carrier gas. The reaction products were propene, allene and aldimines. The allene to propene ratio changed considerably with the third substituent on the N atom. At conversions in the range 13-55%, the consumption of the amines showed first-order kinetics. The following Arrhenius parameters [A (s-1) and Ea (kJ mol-1)] were obtained from the rate coefficients: diallyl-tert-butylamine, log  A = 10·32 ± 0·12, Ea = 139 ± 2; diallylneopentylamine, log A = 12·87 ± 0·26, Ea = 168 ± 3; allylpropargyl-tert-butylamine, log A = 10·23 ± 0·18, Ea = 126 ± 2; allylpropargyltosylamine, log A = 13·05 ± 0.36, Ea = 197 ± 5; and allylpropargylphenylamine, log A = 12·10 ± 0·35, Ea = 162 ± 4. Polar, six-center cyclic transition states are suggested for the elimination of propene and allene, via non-concerted bond breaking-bond forming mechanisms. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0044-8249
    Keywords: Komplexe mit Schwefelliganden ; ortho-Metallierung ; Palladiumverbindungen ; Sulfoxide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 860-866 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Application of MNDO, AM1, PM3, MNDO/H, and MNDO/M methods to a set of compounds with intramolecular hydrogen bonds suggested that none of these methods accurately modeled the characteristics of the hydrogen bonds. Since the MNDO/H and MNDO/M methods work well for intermolecular hydrogen bonds, we followed their example and modified MNDO for intramolecular hydrogen bonds by altering the empirical core-core repulsion energy function for all pairs of atoms involved in intramolecular O-H—O bonds. The resulting modified method models the behavior of these bonds quite well, especially as regards their geometry and the barrier to proton transfer. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 14 (1993), S. 922-927 
    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 quantitative comparative analysis of molecular electrostatic potential (MEP) distributions generated from different wave functions was carried out. Wave functions were computed by using MNDO, AMl, STO-3G, 3-21G, 4-31G, 6-31G, 4-31G*, 6-31G*, and 6-31G** methods. Ten different compounds, which include usual atoms and groups of biomolecules, such as hydroxyl, carbonyl, amine, amide, imine, double and triple bonds, and heteroaromatic rings, were studied. For each compound, MEP values in the points of a common 3-D grid were computed; thereafter, the similarity between each pair of MEP distributions generated by different methods was assessed. Similarities were measured using the Spearman rank correlation coefficient. A similarity matrix was obtained for each compound. Similarity matrices were averaged and a hierarchical cluster analysis was carried out to classify the different quantum chemical methods. In the compounds studied, the main conclusion is the negligible difference between the pattern of MEP distributions generated from all split valence basis sets (with and without polarization functions). © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 183-189 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: In the forerunner of this article, we described a MNDO modification designed for studies of compounds with intramolecular O—H…O hydrogen bonds. Here, we report the further verification of the modification by means of its application to 14 compounds not considered in its development. Comparison of the calculated structural parameters and proton transfer characteristics with available experimental or ab initio results, and with those obtained using MNDO, AM1, MNDO/H, MNDO/M, and PM3, supports the validity of the new modification for prediction of hydrogen bond characteristics. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0570-0833
    Keywords: complexes with sulfur ligands ; ortho-metalation ; palladium compounds ; sulfoxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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