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  • Digitale Medien  (409)
  • Online-Ressource
  • 2025-2025
  • 1980-1984  (409)
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  • 1920-1924
  • 1905-1909
  • 1983  (199)
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  • Physical Chemistry  (243)
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  • Digitale Medien  (409)
  • Online-Ressource
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  • 2025-2025
  • 1980-1984  (409)
  • 1935-1939
  • 1920-1924
  • 1905-1909
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  • 101
    Digitale Medien
    Digitale Medien
    Kinetics of oxidative coupling of phenols: Oxidation of naphthols by alkaline hexacyanoferrate (III) (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 197-203 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The oxidation of naphthols by alkaline hexacyanoferrate(III), at constant ionic strength, gave coupled products. The rate of the reaction was dependent on the first powers of the concentrations of substrate, oxidant, and alkali. The activation energies were 31.8 and 34.5 kJ/mol for α naphthol and β naphthol, respectively. The reaction pathway was via the formation of a radical intermediate, which was detected by electron spin resonance spectroscopy.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150209
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  • 102
    Digitale Medien
    Digitale Medien
    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983) 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150301
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  • 103
    Digitale Medien
    Digitale Medien
    Kinetics of dialin thermolysis (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 219-233 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The liquid-phase thermolysis of 1,2-dihydronaphthalene was studied in a batch reactor in the range of 350-400°C. The measured product distributions were in good agreement with calculations based on a free-radical scheme with rate constants estimated by thermochemical methods. The kinetic calculations were carried out by numerical integration and by the long-chain approximation (LCA), which yielded a closed-form solution.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150303
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  • 104
    Digitale Medien
    Digitale Medien
    Recommendations for measuring second-order rate constants and kinetic solvent isotope effects on acid-catalyzed reactions (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 235-248 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Kinetic solvent isotope effects (KSIE) were measured for the hydrolyses of acetals of benzaldehydes in aqueous solutions covering the pH (pD) range of 1-6. For p-methoxybenzaldehyde diethyl acetal, kD+/kH+ = 1.8-3.1, depending on the procedure used to calculate the KSIE and on the pH (pD) range used as the basis for kH+(kD+). It is shown that this variation is an experimental artifact, and is a characteristic of KSIE measurements in general. It is recommended that kL+ be calculated from a least-squares fit of data to the equation kobs = kL+[L+], and that the KSIE be reported as kD+/kH+. The limitation remains, however, that the KSIE measured for a variety of substances over quite different pH (pD) ranges may not be comparable to more than ℜ20%. The source of these observations is discussed in terms of small changes in the activity coefficient ratios (a specific salt effect), including the solvent isotope effect on the activity coefficient ratio [eq. (3)].
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150304
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  • 105
    Digitale Medien
    Digitale Medien
    Gas-phase elimination kinetics of 1-substituted ethyl acetates. Effect of polar substituents at the α carbon of secondary acetates (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 205-218 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The gas-phase elimination of several polar substituents at the α carbon of ethyl acetates has been studied in a static system over the temperature range of 310-410°C and the pressure range of 39-313 torr. These reactions are homogeneous in both clean and seasoned vessels, follow a first-order rate law, and are unimolecular. The temperature dependence of the rate coefficients is given by the following Arrhenius equations: 2-acetoxypropionitrile, log k1 (s-1) = (12.88 ± 0.29) - (203.3 ± 2.6) kJ/mol (2.303RT)-1; for 3-acetoxy-2-butanone, log ±1(s-1) = (13.40 ± 0.20) - (202.8 ± 2.4) kJ/mol (2.303RT)-1; for 1,1,1-trichloro-2-acetoxypropane, log ℜ1 (s-1) = (12.12 ± 0.50) - (193.7 ± 6.0) kJ/mol (2.303RT)-; for methyl 2-acetoxypropionate, log ℜ1 (s-1) = (13.45 ± 0.05) - (209.5 ± 0.5) kJ/mol (2.303RT)-1; for 1-chloro-2-acetoxypropane, log ℜ1 (s-1) = (12.95 ± 0.15) - (197.5 ± 1.8) kJ/mol (2.303RT)-1; for 1-fluoro-2-acetoxypropane, log ℜ1 (s-1) = (12.83 ± 0.15)- (197.8 ± 1.8) kJ/mol (2.303RT)-1; for 1-dimethylamino-2-acetoxypropane, log ℜ1 (s-1) = (12.66 ± 0.22) -(185.9 ± 2.5) kJ/mol (2.303RT)-1; for 1-phenyl-2-acetoxypropane, log ℜ1 (s-1) = (12.53 ± 0.20) - (180.1 ± 2.3) kJ/mol (2.303RT)-1; and for 1-phenyl-3-acetoxybutane, log ℜ1 (s-1) = (12.33 ± 0.25) - (179.8 ± 2.9) kJ/mol (2.303RT)-1. The Cα—O bond polarization appears to be the rate-determining process in the transmition state of these pyrolysis reactions. Linear correlations of electron-releasing and electron-withdrawing groups along strong σ bonds have been projected and discussed. The present work may provide a general view on the effect of alkyl and polar substituents at the Cα—O bond in the gas-phase elimination of secondary acetates.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150302
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  • 106
    Digitale Medien
    Digitale Medien
    Kinetics of electrophilic brominations. Mechanistic significance of the third-order term (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 249-266 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The rates of electrophilic bromination of various donors follow complex kinetics which include both first-order and second-order dependences on bromine, especially in the less polar solvents. The second-order rate constant ks and the third-order rate constant kt are evaluated for alkene bromination in carbon tetrachloride, and they are compared to those already listed for the electrophilic brominations of substituted styrenes, arenes, and metal carbonyls in the extant literature. Despite the varying magnitudes of the second- and third-order rate constants for these diverse donors (and in different solvents), the ratio log(ks/kt) is remarkably invariant. The mechanistic implication of this unique observation is discussed in the context of charge transfer interactions which are common to the activated complexes in the electrophilic brominations of various donors.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150305
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  • 107
    Digitale Medien
    Digitale Medien
    Rate constants for the bimolecular self-reaction of cyano-substituted alkyl radicals in solution (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 267-279 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cyano-substituted methyl radicals (cyanomethyl-hand 2-cyano-2-propyl radicals) and syn-and anti-1-cyano-allyl radicals were generated, and their recombination kinetics in solution were investigated between -50 and +50°C by time-resolved electron-spin-resonance spectroscopy. The comparison of the activation energies for recombination with the activation energies of the solution viscosities proves that the dimerizations of the radicals are diffusion controlled with rate constants on the order of 108-109M-1·s-1. In the case of cyanomethyl radicals an additional pseudo-first-order process, hydrogen abstraction, was detected and analyzed kinetically. Product analyses support the kinetic measurements.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150306
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  • 108
    Digitale Medien
    Digitale Medien
    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983) 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150401
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  • 109
    Digitale Medien
    Digitale Medien
    The kinetics of the gas phase decomposition reactions of the hexafluoro-t-butoxy radical (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 293-303 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hexafluoro-t-butoxy radicals have been generated by reacting fluorine with hexafluoro-2-methyl isopropanol: Over the temperature range of 406-600 K the hexafluoro-t-butoxy radical decomposes exclusively by loss of a CF3 radical [reaction (-2)] rather than by loss of a CH3 radical [reaction (-1)]: The limits of detectability of the product CF3COCF3, by gas-chromatographic analysis, place a lower limit on the ratio k-2/k-1 of ∼80. The implications of this finding in relation to the reverse radical addition reactions to the carbonyl group are briefly discussed.A thermochemical kinetic calculation reveals a discrepancy in the kinetics and thermodynamics of the decomposition and formation reactions of the related t-butoxy radical:
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150308
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  • 110
    Digitale Medien
    Digitale Medien
    The kinetics of the addition of alkyl radicals to carbonyl groups. Part I. The addition of methyl radicals to hexafluoroacetone in the gas phase. The formation of the hexafluoro-t-butoxy radical (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 281-291 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By pyrolyzing di-t-butyl peroxide over the temperature range of 405-450 K in the presence of hexafluoroacetone the kinetics of the addition reaction (1), CH3 + (CF3)2CO→; (CF3)2C(Ȯ)CH3, have been studied. Detailed analyses have shown that the principal product of the adduct radical, (CF3)2C(Ȯ)CH3, is CF3COCH3 from reaction (2), (CF3)2C(Ȯ)CH3 → CF3COCH3 + CF3. The rate constant of the addition reaction was determined to be k1(dm3/mol·s) = (1.1 ± 4.0) + 109 exp(-(3680 ± 480)/T) over the temperature range 405-450 K, based on the value k3 = 2.2 × 1010 dm3/mol·s for reaction (3), 2CH3 → C2H6. The results are discussed in relation to existing data for radical additions to carbonyl groups.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150307
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  • 111
    Digitale Medien
    Digitale Medien
    The oxidation of HI at low temperatures and the heat of formation of HO2 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 323-339 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the oxidation of hydrogen iodide (HI + O2) at low temperature (414-499 K) in the gas phase by the method of iodination kinetics is complicated by a heterogeneous reaction between hydrogen iodide and oxygen. Present work leads to an upper limit for the bimolecular rate constant k1 for the first and rate-determining step These data are combined with an estimated A factor A1 = 109.3±0.2 L/mol·s (assuming a tight linear I···H···O -  transition state), to calculate the lower limit of the activation energy for the forward reaction E1. This leads to a minimum value for the heat of formation of the HO2 radical, ΔHf298°(HO2) 〈 3.0 kcal/mol.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150403
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  • 112
    Digitale Medien
    Digitale Medien
    Rate constant and products of the reaction CS2 + OH in the presence of O2 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 631-645 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of OH radicals with CS2 has been investigated by the application of Fourier transform infrared spectroscopy using both photolytic and nonphotolytic competitive techniques in a 420-L reaction chamber at different pressures over the temperature range of 264-293 K. The measured effective rate constant was found to be dependent on total pressure, temperature, and the mole fraction of O2 present in the system. The products of the reaction were found to be COS and SO2 with one molecule of each being formed for every reacted CS2. A value of (2.7 ± 0.6) × 10-12 cm3/molecule·s was obtained as effective rate constant for the reaction at 293 K in 760 torr of synthetic air.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150705
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  • 113
    Digitale Medien
    Digitale Medien
    An FTIR study of the mechanism for the reaction HO + CH3SCH3 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 647-654 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Product studies were made using the Fourier transform infrared method in the uv (300-400-nm) photolysis of mixtures containing CH3SCH3, C2H5ONO, and NO in ppm concentrations in 700 torr of O2-N2 diluent. Methyl thionitrite, CH3SNO, arising from the reaction CH3S + NO, was detected as an intermediate product. In addition, the yields of the major sulfur-containing products SO2 and CH3SO3H coincided with those of the oxidation of the CH3S radicals generated directly by the photodissociation of CH3SNO. The formation of CH3S in the HO-initiated oxidation of CH3SCH3 in the presence of NO suggests a reaction scheme involving the H-abstraction reaction HO + CH3SCH3 → CH3SCH2 + H2O as the primary step.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150706
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  • 114
    Digitale Medien
    Digitale Medien
    Rate constants of the reaction of ozone with trans-1,2-dichloroethene and vinyl chloride in air (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 655-668 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Kinetic studies on reactions of ozone with trans-1,2-dichloroethene (DCE) and vinyl chloride (VC) were performed in air. In the presence of scavengers of radicals, such as CH3CHO, the rates for both reactions are second order (first order in each reactant). Observed rate constants are (1.80 ± 0.29) X 10-19 cm3/molecule·s for DCE and (2.45 ± 0.45) × 10-19 cm3/molecule·s for VC. In the presence of CH3CHO, propene ozonide \documentclass{article}\pagestyle{empty}\begin{document}$ ({\rm CH}_3 \overline {{\rm CHOOCH}_2 {\rm O}}) $\end{document} was observed as a product in the case of VC. Peroxyformic acid (HC)O(OOH) was detected in both reactions. The Criegee mechanism was proposed to play a major role in the reaction of ozone with chloroolefins. The branching ratio of O3 + CH2=CHCl → CH2OO + HCOCl (6a), CHClOO + HCHO (6b) was obtained as 76:24, and the fraction of the stabilized CH2OO was estimated to be 0.25 of that produced in reaction (6a).
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150707
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  • 115
    Digitale Medien
    Digitale Medien
    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983) 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150801
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  • 116
    Digitale Medien
    Digitale Medien
    Kinetics and mechanism of osmium(VIII)-catalyzed oxidation of D-proline and L(-)-methionine by hexacyanoferrate(III) (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 669-676 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The osmium(VIII)-catalyzed oxidation of D-proline and L(-)-methionine by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The reactions follow kinetics different from those of the oxidation of many amino acids investigated earlier, being first order in hexacyanoferrate(III) and osmium(VIII). The order in proline or methionine and OH- decreases from unity to zero at higher concentrations of proline or methionine and OH-, respectively. A mechanism consistent with the kinetic data is proposed and discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150708
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  • 117
    Digitale Medien
    Digitale Medien
    Sensitivity analysis and parameter estimation in dynamic modeling of chemical kinetics (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 677-696 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new approach to the dynamic modeling of chemical kinetics is presented. The technique is based on systematic planning of computer experiments, which allows an empirical model for the computed responses to be developed in the space of parameters. The empirical equations which are obtained provide complete information on the sensitivities with respect to various rate constants, disclosing their interrelationships. Utilization of these equations instead of numerical integration of the differential equations associated with the chemical reactions makes parameter estimation a trivial task. As a consequence the adequacy of the mechanism can be tested. The technique is applied to the thermal decomposition of propane.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150709
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  • 118
    Digitale Medien
    Digitale Medien
    Kinetic analysis of an extended single-path sequence of first-order reactions. The reaction of mesitonitrile in sulfuric acid (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 697-703 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The system of a sequence of five first-order reactions, A → B → C → D → E → F, has been analyzed kinetically. An actual example is proposed in the reaction of mesitonitrile in 89.8% (w/w) sulfuric acid at 98.3°C. The analysis provides estimates of concentration ratios as functions of time, and the progress of the buildup and decay of the intermediate species can be monitored. The kinetics have been measured for the hydration of mesitonitrile, the hydrolysis of mesitamide, and the sulfonation of mesitylenesulfonic acid in 89.8% sulfuric acid. The calculated values of the concentration ratios of mesitylenedisulfonic acid as a function of time were satisfactorily close to those found in experiment.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150802
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  • 119
    Digitale Medien
    Digitale Medien
    Theoretical rate constant calculations for O(3P) with saturated hydrocarbons (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 705-719 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Theoretical rate constants have been calculated for O(3P) with five saturated hydrocarbons, CH4, C2H6, C3H8, iso-C4H10, and neo-C5H12. The method of choice is bond energy-bond order (BEBO) with activated complex theory (ACT). Because the BEBO method is empirical, O(3P) + CH4 is evaluated first, and the theoretical results are compared to more rigorous calculations and to the empirical transition state method. Comparisons are also made between predictions and experimental results. All of these comparisons show that the BEBO-ACT method gives results which are consistent with experiment and other theory. Because the method is successful, the other four cases are then considered. Ambiguity arises for the higher hydrocarbons from the problem of internal rotations in the activated complexes, and three cases are evaluated. Best agreement with experiment is obtained if the primary rotor(s) in the complexes are considered to be free. Predictions of rate constants are made from 500 to 2500 K. Throughout the discussion issues of theory which are common to any ACT calculation from any method of potential energy evaluation (LEP, LEPS, or ab initio quantum mechanics) are featured.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150803
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  • 120
    Digitale Medien
    Digitale Medien
    Effects of ring strain on gas-phase rate constants. I. Ozone reactions with cycloalkenes (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 721-731 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Rate constants for the gas-phase reactions of O3 with a series of cycloalkenes and with cis-2-butene have been determined at 297 ± 1 K. The rate constants obtained were (in units of 10-16 cm3/molecule·s): cis-2-butene, 1.38 ± 0.16; cyclopentene, 2.75 ± 0.33; cyclohexene, 1.04 ± 0.14; cycloheptene, 3.19 ± 0.36; 1,3-cyclohexadiene, 19.7 ± 2.8; 1,4-cyclohexadiene, 0.639 ± 0.074; bicyclo[2.2.1]-2-heptene, 21.4 ± 3.5; bicyclo[2.2.1]-2,5-heptadiene, 46.8 ± 12.9; and bicyclo[2.2.2]-2-octene, 0.728 ± 0.090. These data for cis-2-butene, cyclopentene, and cyclohexene are compared with previous literature data, and the effects of ring strain on the rate constants are discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150804
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  • 121
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    Digitale Medien
    Effects of diffusion on the self-termination kinetics of isopropylol radicals in solution (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 733-757 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Rate constants for the bimolecular self-reaction of isopropylol radicals [(CH3)2ĊOH] in various solvents are determined as functions of temperature by kinetic electron spin resonance. For hydrocarbon solvents they are well described by theoretical equations for reactions controlled by translational diffusion if diffusion coefficients of 2-propanol, a constant reaction distance, and a spin statistical factor of 1/4 are applied. Deviations from 2kt ∼ D at high diffusion constants agree with trends expected from recent theoretical models. For hydrogen-bonding solvents large negative deviations are observed. They are attributed to steric constraints and slower rotational diffusion of radical-solvent aggregates. The disproportionation-to-combination ratio of isopropylol increases with solvent viscosity. As previously for tert-butyl, this is explained by anisotropic reorientation during encounters. Further, rate data are given for the decarbonylation of the 2-hydroxy-2-methylpropanoyl radical and for several hydrogen abstraction reactions of isopropylol.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150805
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  • 122
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    Digitale Medien
    Direct conversion of synthesis gas to light hydrocarbons on heterogeneous catalysts (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 759-774 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Six catalysts consisting of mixtures of catalysts for methanol synthesis and its conversion to hydrocarbons were prepared by mechanical mixing, impregnation, and coprecipitation, followed by extrusion. Phase changes occurring during various stages of preparation and after use were followed by x-ray diffraction. The catalysts were found to be nontrivial bifunctional catalysts which selectively convert synthesis gas directly to low molecular weight hydrocarbons in the range of C1 to C4. Methanol and dimethylether were detected as intermediates. Olefins were formed, and their further hydrogenation yielded products with high paraffinic content. Carbon dioxide retards the conversion of synthesis gas to hydrocarbons, whereas steam retards the hydrogenation of olefins. On heating the commercial zinc chromite catalyst, dehydration, reduction, and solid-state reactions occur with the formation of ZnO-ZnCr2O4 solid solution. Exchanging cations within the zeolite component did not affect the space lattice, but these ions tend to occupy special sites, and during service more order was detected. Copper ions tend to diffuse in ZnO, forming a solid solution, and during service metallic copper was produced.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150806
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  • 123
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    Digitale Medien
    The kinetics and mechanisms of the gas-phase pyrolysis of ethyl 4-bromobutyrate. The ion-pair mechanism revisited (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 795-803 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The gas-phase pyrolysis of ethyl 4-bromobutyrate has been investigated in a static system over the temperature range of 354.6-374.7°C and the pressure range of 51-126 torr. The elimination reaction in seasoned vessels and in the presence of at least twofold of a chain radical inhibitor is homogeneous, unimolecular, and obeys a first-order rate law. The rate coefficients are given by the Arrhenius equation log k1(s-1) = (13.31 ± 0.82) - (205.1 ± 8.6)kJ/mol/2.303RT. The partial rates for the parallel eliminations to normal dehydrobromination, lactone formation, and bromobutyric acid product have been estimated and reported. The carboethoxy substituent of the bromoester has been found to assist anchimerically the elimination process, where dihydrobromination and lactone formation arise from an intimate ion-pair mechanism.
    Zusätzliches Material: 9 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150808
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  • 124
    Digitale Medien
    Digitale Medien
    Kinetics and mechanism of reaction of p-methoxystyrene and tetracyanoethylene. II. Effect of pressure (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 805-814 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of p-methoxystyrene and TCNE is studied in 50% CHCl3-50% CCl4 (v/v) at 25°C at high pressures up to 1000 bar by following the disappearance of the absorbance at 600 nm due to the EDA complex. By using the mixed solvent, equations required for the high-pressure kinetics are simplified. The volume of activation is -42 to -46 cm3/mol for the 1,4-cycloaddition and -55 cm3/mol for the 1,2-cycloaddition. The activation volume for the 1,4-cycloreversion is assumed to be -8 to -12 cm3/mol based on a previous study on a similar system. The rate of the cycloreversion process is affected by solvent polarity. The rate of the 1,2-cycloaddition is influenced by solvent more significantly than that of the 1,4-cycloaddition. It is concluded that the transition state is polar in both cycloadditions and that its zwitterionic character is much stronger in the 1,2-cycloaddition.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150809
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  • 125
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    Digitale Medien
    Kinetic and mechanistic studies of oxidation of alanine and phenylalanine by sodium N-chlorobenzene sulfonamide (chloramine-B) in hydrochloric acid medium (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 775-793 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of oxidation of alanine and phenylalanine by sodium N-chlorobenzene sulfonamide (CAB) has been investigated at 30°C in two ranges of acid concentrations. The reactions follow identical kinetics for both amino acids. At low acid concentration (0.03-0.10M), simultaneous catalysis by H+ and Cl- ions is noted. The rate shows a first-order dependence on [CAB], but is independent of [substrate]. A variation of the ionic strength or the dielectric constant of the medium or the presence of the added reaction product benzene sulfonamide (BSA) has no pronounced effect on the rate.At [HCl] 〉 0.2M, the rate is independent of [H+], but shows a first-order dependence on [CAB] and a fractional-order dependence on [amino acid]. The addition of BSA or Cl- ions, or a change in the ionic strength of the medium has no influence on the rate. Upon decreasing the dielectric constant of the medium, the rate increased, indicating positive ion-dipole interaction in the rate-determining step. The reaction was studied at different temperatures, and activation parameters have been computed. Rate laws in agreement with experimental results have been derived. Suitable mechanisms to account for the observed kinetics are proposed. The rate constants obtained from the derived rate laws as [H+], [Cl-], and [substrate] vary are in excellent agreement with the observed rate constants, thus justifying the proposed rate laws and hence the suggested mechanistic schemes.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150807
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  • 126
    Digitale Medien
    Digitale Medien
    Kinetics and equilibria in the system Br + t-BuO2H ⇆ HBr + t-BuO2. OH bond dissociation energy in t-BuO2-H (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 815-822 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics and equilibria in the system Br + t-BuO2H ⇆ HBr + t-BuO2· have been measured in the range of 300-350 K using the very low pressure reactor (VLPR) technique. Using an estimated entropy change in reaction (1) ΔS1 = 3.0 ± 0.4 cal/mol·K together with the measured ΔG1, we find ΔH1 = 1.9 ± 0.2 kcal/mol and DHº (t-BuO2-H) = 89.4 ± 0.2 kcal/mol ΔHf·(tBuO2·) = 20.7 kcal/mol and DHº (t-Bu-O2) = 29.1 kcal/mol. The latter values make use of recent values of ΔHf·(t-Bu) = 8.4 ± 0.5 kcal/mol and the known thermochemistry of the other species. The activation energy E1 is found to be 3.3 ± 0.6 kcal/mol, about 1 kcal lower than the value found for Br attack on H2O2. It suggests a bond 1 kcal stronger in H2O2 than in tBuO2H.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150810
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  • 127
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    Digitale Medien
    Studies in nickel(IV) chemistry. Electron transfer kinetics of the reaction between tris(dimethylglyoximato)nickelate(IV) and hexacyanoferrate(II) in aqueous medium (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 823-833 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of electron transfer from hexacyanoferrate(II) to tris(dimethylglyoximato)-nickelate(IV), Ni(dmg)32-, to produce Fe(CN)63- and Ni(dmgH)2, follows a pseudo-first-order disappearance in the Ni(IV). The pseudo-first-order rate constants kobs are linearly dependent on [Fe(CN)64-]0 in a fiftyfold range of 2 × 10-4-1 × 10-2M, and the average values of kobs/[Fe(CN)64-]0 range from 194M-1·s-1 at pH = 5.20 to 0.2M-1·s-1 at pH = 9.07 in aqueous medium at 35°C and μ = 0.57M. Results are interpreted in terms of a probable mechanism involving rate-determining outer sphere one-electron transfer steps from the reductant and one-protonated reductant species to the unprotonated and one-protonated Ni(IV) species present in solution. The more electrophilic one-protonated reductant species apparently reacts several orders of magnitude faster than the unprotonated one.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150811
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  • 128
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    Digitale Medien
    Reaction of CF3 radicals with H2O and D2O (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 835-844 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of CF3 radicals with H2O (D2O) has been studied over the range of 533-723 K using the photolysis and the pyrolysis of CF3I as the free radical source. Arrhenius parameters for the reactions \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm CF}_3 + {\rm X}_2 {\rm O\buildrel{k_x}\over{\to}CF}_3 {\rm X} + {\rm OX} $$\end{document} where X = H or D, relative to CF3 radical recombination are given by \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} {\rm log}k_{\rm H} /k_c^{1/2} = (5.12 \pm 0.11) - (16,804 \pm 335)/\theta \\ {\rm log}k_{\rm D} /k_c^{1/2} = (5.03 \pm 0.16) - (17,803 \pm 456)/\theta \\ \end{array} $$\end{document} where k/kc1/2 is in cm3/2/mol1/2·s1/2 and θ = 2.303RT/cal/mol. The activation energy and the primary kinetic isotope effect have been compared with those derived from the BEBO method.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150812
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  • 129
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    Digitale Medien
    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983) 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150901
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  • 130
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    Digitale Medien
    Koopmans' theorem ionization potentials of methyl and silyl halides, chalcogenides, amines, and phosphines: An ab InitioSCF study (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 9-14 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Koopmans' theorem ionization potentials have been calculated for a series of hydrides, methyls, and silyls HnX, (CH3)nX, and (SiH3)nX (X = F, Cl, n = 1; X = O, S, n = 2; X = N, P, n = 3), together with some mixed species (MH3)nXH3-n (X = N, P; M = C, Si) using ab initio SCF methods. The calculated values give excellent agreement with experimental values without the inclusion of d functions. For the chlorides, HCl, CH3Cl, and SiH3Cl, the values vary rather little over a wide range of basis sets, and are unaffected by the inclusion of d functions.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040103
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  • 131
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    Digitale Medien
    Restricted Hartree-Fock approximation. II. Computational aspects of the direct minimization procedure (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 41-47 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A RHF energy minimization procedure based on the treatment outlined in Part I of this series of articles is presented. Test calculations performed on several closed- and open-shell systems show that the present procedure is definitely superior to the conventional SCF methods. In particular, the convergence of this procedure is ensured, the rate of convergency is high, and the computational cost of each cycle is low.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040107
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  • 132
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    Digitale Medien
    Ab initio studies on calicene (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 53-57 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Optimum geometries of planar and 90°-twisted C2v calicene are calculated with single-configuration STO-3G and 3-21-G wavefunctions. The barrier to ring-ring rotation is computed. Bond alternation is pronounced in the planar form and decreases in the twisted form, while dipolar character increases on twisting.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040109
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  • 133
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    Digitale Medien
    Comparison of RHF, NDDO, and MOM molecular one-electron expectation values calculated using weighted and unweighted STO-NG (ω) basis functions (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 48-52 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The effect of basis functions on molecular one-electron property expectation values calculated by approximate methods is examined using weighted and unweighted least-squares Gaussian-type orbital function expansions of Slater-type orbital functions.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040108
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  • 134
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    Digitale Medien
    Ab initio studies of a proposed mechanism for N-Nitrosamine formation (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 68-72 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The geometry of a proposed intermediate (α-dialkylamino nitrite ester) of N-nitrosamine synthesis from nitrites is studied by ab initio SCF methods. The energy of a zwitterion is calculated and found to be high.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040111
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  • 135
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    Digitale Medien
    Ground states of molecules. 56. See Part 55 in this series: M. J. S. D. Dewar and S. Olivella, J. Am. Chem. Soc., 101, 4958 (1979).MNDO calculations for molecules containing sulfur (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 84-103 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: MNDO has been extended to sulfur, but without inclusion of 3d AOs. Calculations are reported for heats of formation, geometries, dipole moments, and ionization energies of a variety of sulfur-containing molecules. The average discrepancy between calculated and observed heats of formation is larger than for compounds of other elements, a difference probably due, at least partly, to the lower accuracy of the thermochemical data for sulfur compounds. The calculated dipole moments agree well with experiment as do the calculated ionization energies, except for those corresponding to ionization from sulfur “lone-pair” orbitals which are too high by ca. 1 eV, probably as a result of the neglect in NDDO of interactions between inner and valence shell orbitals. As in the case of other third-period elements, the calculated heats of formation of compounds of sulfur in its higher valence states (SIV, SVI) were too positive by large amounts, due presumably to the neglect of 3d AOs.
    Zusätzliches Material: 10 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040113
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  • 136
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    Digitale Medien
    Progress in theoretical organic chemistry, volume 3, L. Radom et al. Elsevier, New York, 1982. Price: $103 (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 123-123 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040117
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  • 137
    Digitale Medien
    Digitale Medien
    Masthead (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983) 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040201
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  • 138
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    Digitale Medien
    Standard deviation in reduced errors (SDRE): A criterion to assess the relative overall quality of approximate wavefunctions (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 150-153 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The standard deviation in reduced errors (SDRE) quantitatively measures the similarity between an approximate and exact wavefunction. It is the Euclidean distance between the vector of the one-electron property expectation values calculated using the approximate and exact expectation values.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040205
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  • 139
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    Digitale Medien
    Dipole polarizability derivatives calculated by the Kirkwood method (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 170-174 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Derivatives, with respect to the symmetry coordinates, of the components of the dipole polarizabilities of HF, H2O, and CH4 are calculated using the Kirkwood method and a generalization of that method. The results for the bond-stretching derivatives are in reasonable agreement with those found by finite field calculations; those for angle changes are of the correct sign, but their magnitudes are in poor agreement with the finite field ones. The results are also analyzed using a four-parameter bond polarizability model.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040208
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  • 140
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    Digitale Medien
    Properties of excited states of aromatic rings containing nitrogen (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 410-418 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Quantum chemical calculations with the semiempirical molecular orbital (MO) method SINDO1 were performed on excited states of the following five- and six-membered heterocycles containing nitrogen: imidazol, pyrazol, pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine. The geometries and adiabatic excitation energies of T1, S1, S2 were calculated. We also present charges, bond orders, and dipole moments. Consequences of these results for UV spectroscopic data are discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040317
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  • 141
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    Digitale Medien
    Masthead (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983) 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040401
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  • 142
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    Digitale Medien
    Theoretical conformational analysis of the Gramicidin a transmembrane channel. I. Helix sense and energetics of head-to-head dimerization (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 461-469 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Conformational energy calculations are presented for the head-to-head dimerized β helices for Gramicidin A transmembrane channel structures. The calculations take into account both left- and right-handed β helices, and various side-chain conformations. The energetics of the dimerization is studied by considering various docking geometries. It is concluded from these vacuum-energy calculations that the lowest energy conformation for the channel dimer is that comprised of left-handed β helices.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040403
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  • 143
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    Digitale Medien
    Substituent effects on the charge density in the formyl group (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 15-22 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: SCF wavefunctions with similar extended Gaussian bases for the series HCOX with X = H, OH (syn and anti), NH2, CN, and F yield closely similar charge deformation density maps in the formyl region of all six molecules. The differences, measured by moments of partitioned atomic deformation densities, correlate almost linearly with the Hammett substituent parameters σI and σR of the several substituents X. However, systematic deviations, especially in the carbon fragment, suggest the need for modified values of the inductive parameters σI for the correlation of these molecular charge densities.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040104
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  • 144
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    Digitale Medien
    Restricted Hartree-Fock approximation. I. Techniques for the energy minimization (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 33-40 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: We present a new procedure for direct minimization of the RHF energy, which presents advantages over SCF methods with respect to convergence rate and computational cost. In this procedure we combine several techniques with the aim of obtaining best directions and step lengths for the iterative search for a minimum of the energy. In this article we develop the theory. Therefore, we analyze the variational function; we present a short description of the minimization techniques and we discuss in detail the way in which they are to be used. The computational aspects of the procedure will be treated in the following article.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040106
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  • 145
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    Digitale Medien
    Symmetry properties of chemical graphs. V. Internal rotation in XY⋅3XY⋅2XY3 (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 73-83 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Structures XY⋅3XY⋅2XY3 of symmetry C2v (of which propane is an example) are examined and the rearrangement due to the internal rotation of the end groups XY3 studied. The isomerization graph is constructed, various forms of which are displayed and the symmetry of which has been determined. The order of the group is 72. There are nine prime (irreducible) representations (4A + E + 4G) with the following partitioning of the elements into classes: 1, 42, 62, 9, 122, 18. When the mechanism for rearrangement is generalized to include enantiomers, a duplex graph is produced with the order of the group 144 which is isomorphic to the group S2(S3,S2) (generalized wreath product of the symmetric group S2 and S3). The corresponding graph has been constructed and displayed in one of more symmetrical forms. Isomorphism of groups of order 144 is discussed and a procedure is outlined in which correspondence between distinctive combinatorial objects is established by inducing permutations of m elements from available permutations of n elements. The scheme is based on selection of suitable graph invariants in one system and their labeling as m objects which form the basis for representation of the symmetry for the other system.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040112
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  • 146
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    Digitale Medien
    A fast algorithm for calculation of the distance matrix of a molecule (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 110-113 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A rapid method is described for calculating the number of bonds on the shortest path between each two pairs of atoms of a molecule.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040115
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  • 147
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    Digitale Medien
    On the general transformation from molecular geometric parameters to cartesian coordinates (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 136-141 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: This article presents a general method and accurate algorithm for calculating the Cartesian coordinates (xa, ya, za) from an arbitrary triple of distances r(a,i), angles, θ(a,j,k), or dihedral angles φ(a,l,m,n), specifying the position of the nucleus a relative to nuclei i,⃜, n with known Cartesian coordinates. There is a brief discussion of the requirements on the 3N-6 geometric parameters in order for them to determine the shape of an N-atomic molecule.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040203
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  • 148
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    Digitale Medien
    Divinylketone: Conformational preferences. Molecular geometry and vibrational force field in the ground state (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 142-149 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The conformational preferences of the molecule 1,4-pentadien-3-one (divinylketone) have been studied by ab initio molecular orbital calculations and discussed in terms of interaction between molecular fragments. The calculations predict a molecular ground state having a fully coplanar s-cis, s-cis conformation. In addition, we find three other structures that represent local minima on the energy surface. These are a fully coplanar s-cis, s-trans form, and two nonplanar s-trans, s-trans forms having symmetries C2 and C1h, respectively. The energies of these forms relative to the ground state are 7.5, 19.2, and 35.9 kJ/mol, respectively. The coplanar s-trans, s-trans form represents a saddle point on the energy surface. All conformers and the saddle point have been completely geometry optimized by the gradient technique. For the ground state a complete in-plane harmonic force field has been evaluated.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040204
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  • 149
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    Digitale Medien
    Ground states of molecules. 53.For part 52, see ref. 1.MNDO calculations for molecules containing chlorine (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 158-169 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: MNDO calculations of heats of formation, dipole moments, ionization potentials, and structures are reported for a wide range of compounds containing chlorine in its characteristic valence state (ClI) and one or more of the elements H, B, Be, C, N, O, and F. The calculated errors in the heats of formation and the dipole moments are not significantly greater than those previously reported for compounds containing no chlorine. First vertical ionization potentials were on average 0.95 eV too high. The ordering of higher cationic states was found to be correct, even for species such as Cl2O, Cl2, and HOCl, where ab initio-Koopmans' theorem calculations predict the incorrect ordering. The calculated energies and geometries of compounds such as CIF3 are qualitatively incorrect, probably because of the lack of 3d atomic orbitals in the orbital basis set.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040207
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  • 150
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    Digitale Medien
    CHARMM: A program for macromolecular energy, minimization, and dynamics calculationsSupported in part by grants from the National Science Foundation and the National Institutes of Health. (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 187-217 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: CHARMM (Chemistry at HARvard Macromolecular Mechanics) is a highly flexible computer program which uses empirical energy functions to model macromolecular systems. The program can read or model build structures, energy minimize them by first- or second-derivative techniques, perform a normal mode or molecular dynamics simulation, and analyze the structural, equilibrium, and dynamic properties determined in these calculations. The operations that CHARMM can perform are described, and some implementation details are given. A set of parameters for the empirical energy function and a sample run are included.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040211
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  • 151
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    Digitale Medien
    Molecular orbital theory of the properties of inorganic and organometallic compounds. 3. STO-3G basis sets for first- and second-row transition metals (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 241-251 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: STO-3G minimal basis sets for first- and second-row transition metals have been formulated and applied to the calculation of equilibrium geometries for a variety of inorganic systems, metal carbonyls, and organometallic compounds. While the overall level of agreement with experiment is not as good as that previously noted for main-group compounds, most trends and many subtle features in geometries are reproduced.
    Zusätzliches Material: 8 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040215
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  • 152
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    Digitale Medien
    Electronic optical activity of (-)-α-phellandrene (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 260-266 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Molecular orbital computations on the sign and magnitude of the Cotton effect of (-)-α-phellandrene (a conjugated diene) and the separate twisted butadiene chromophore were performed using configuration interaction (CI) and the random phase approximation (RPA) methods with a standard minimal basis set of STO/3G orbitals. The relative contributions to the rotatory strength of (-)-α-phellandrene which arise from a twist in the diene unit, the allylic axial bond, and nonplanarity of either one or both of the C=C double bonds were determined by examining various molecular geometries. This theoretical study confirms that the allylic axial substituent/bond provides the largest contribution to the longwavelength Cotton effect. It is found that the rotatory strength arising from distortion of the planar geometry of the double bonds tends to cancel the rotatory strength arising from the sense of twist of the diene unit. The computed energies suggest that molecular geometries where the trisubstituted bond is kept planar, and where twisting is allowed about the cis double bond, may be favored over geometries where torsion is allowed about both double bonds.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040217
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  • 153
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    Digitale Medien
    A technique for determining the symmetry properties of molecular graphs (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 267-275 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A procedure has been devised to determine the automorphism partition and the automorphism group for nondirected graphs. The general approach is to reveal the permutational symmetry by means of its systematic destruction. Symmetry decomposition pathways are created by numerically weighting specific series of vertices. Each pathway leads to a discrete ordered vector. Each pair of pathways that match reveals an element of the automorphism group. Results are presented for two molecular graphs. Further potential applications of this approach to problems of isomorphism, canonical labeling, and structural indexing are discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040218
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  • 154
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    Digitale Medien
    Computer generation of the symmetry elements of nonrigid molecules (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 302-307 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Algorithms and computer programs are developed for generating the symmetry elements of nonrigid molecules. These programs are based on the wreath product formalism for the symmetry groups of nonrigid molecules developed by the present author. Several examples are given to illustrate the procedures. Applications to weakly bound van der Waal complexes synthesized by supersonic beam expansion are also presented.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040304
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  • 155
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    Digitale Medien
    Molecular mechanics with an array processor (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 313-332 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Computer simulation of the mechanics of molecular systems is a popular and powerful method for understanding chemical processes. The complexity of modeled chemical systems has advanced from hard spheres and rare gases to liquid solutions and biomolecules. Such simulations are computationally intensive and thus are limited by the speed of available computers. This article describes the use of specialized hardware, a high-speed floating-point array processor (AP), to dramatically speed up molecular mechanics, in other words molecular dynamics, Monte Carlo, and energy-minimization calculations. Although the array processor is a cost effective solution for computationally intensive problems in terms of hardware (full-time AP usage is equivalent to 2-8 h/day of Cray-1 time), its full speed comes at the expense of programming in a relatively difficult parallel assembly language. Since the architecture of the machine is dramatically different from conventional computers and utilizing its fast speed necessitates using this architecture on the assembly language level, the proper design and implementation of algorithms is critical. The molecular mechanics software design discussed here, consisting of 12,000 lines of C and 7000 lines of AP assembly language code, is quite general and has been used to study systems ranging from rare gases to biomolecules. This implementation yields effective speeds approximately 35 times faster than a dedicated DEC VAX 11/780 computer with floating-point accelerator and optimized VMS FORTRAN, thus allowing simulations to be run in one and a half weeks on the AP which would require a year of dedicated VAX time. The flexibility of the UNIX operating system, whose source code is accessible and can be modified to optimize performance, combined with the modern features of the C language, have made this implementation much easier by providing a convenient and powerful environment in which to imbed the hand-coded AP assembly language modules. Applications to date range from the molecular-dynamic calculation of infrared, Raman, and electronic spectra in gas and liquid solutions to the calculation of thermodynamic quantities for water and the simulation of the molecular dynamics of solution reactions and polypeptides.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040306
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  • 156
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    Digitale Medien
    Interactions of molecules with nucleic acids. VII. Evaluation and presentation of steric contours and molecules in bonding sites (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 366-378 
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    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A technique to generate steric contours is developed and applied to the presentation of molecules that interact with DNA. The contours are generated by a Taylor's expansion in an extrapolation procedure designed to avoid infinite derivatives and correct for reversal in the direction of the drawing of the curve. A solution to the hidden line problem in computer graphics is presented for the case of steric contours ordered in parallel planes. The techniques developed in this article are demonstrated with stereographic orthographic projections for B-DNA, for intercalation complexes of lucanthone and actinomycin-D with DNA, and for the binding of benzo[a]pyrene diol epoxides (BPDEs) to guanine. The latter example illustrates the value of steric contours in demonstrating the lack of fit of BPDEs to B-DNA and by the need to unwind DNA to accommodate this molecule. Electrostatic contours in planes may be generated by this same procedure.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040312
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  • 157
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    Digitale Medien
    A theoretical study of the interaction of monomethylammonium with double-stranded oligonucleotides (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 390-398 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Theoretical computations are performed of the interaction specificities of the monomethylammoniumion with double-stranded oligonucleotides (dPu)n·(dPy)n in the B-DNA conformation. The effects of base sequence and chain length are examined. In short oligomers (n = 2, 3), the interaction energies of the cation are larger in the major groove of (dG)n·(dC)n than in the minor groove of (dA)n·(dT)n. As a consequence of further shaping of the grooves and building up of the phosphates, a marked reversal in the affinities of the cation for the grooves occurs at the (dPu)5·(dPy)5 and the p(dPu)5p·p(dPy)5p levels: it is the binding in the minor groove of the adenine-thymine oligomers that provides then the most favorable interaction energies.It is also shown, at the level of the double helices built from dinucleoside monophosphates, that the interaction of monomethylammonium in the minor groove occurs in specific configurations involving the three NH bonds of the cation, and two successive bases on one strand; this binding is sequence-specific, the order of inherent preferences being (TpA) 〉 (TpT) 〉 (ApA) 〉 (ApT).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040314
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  • 158
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    Digitale Medien
    A water-mediated tautomerism mechanism in formamide and amidine. An ab initio study (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 419-427 
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    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Formamide, formamidic acid, and amidine water complexes were studied using 3-21G fully optimized structures and 6-31G energies. Hydrogen bonding and a water-mediated tautomerism mechanism were examined. The optimized complexes show that relaxation of the monomers has occurred. Hydrogen bond lengths and energies fall within the range of values found using other basis sets and other comparable systems.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040318
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  • 159
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    Digitale Medien
    Through-Space effects on vicinal proton spin-spin coupling constants mediated via hetero atoms: Nonequivalence of cis couplings in five-membered rings (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 438-448 
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    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Theoretical studies are presented, aimed at the elucidation of through-space effects exerted by bridge-head oxygen and nitrogen atoms on cisoidal proton spin-spin coupling constants in 7-hetero-substituted norbornanes. The finite perturbation theory intermediate neglect of differential overlap (INDO) self-consistent field (SCF) molecular orbital (MO) method, modified according to the description given by Barfield [J. Am. Chem. Soc., 102, 1 (1980)], was employed. It is predicted that the known nonequivalence between Jendo-endo and Jexo-exo in norbornanes, which is in part mediated by the bridgehead methylene group (Barfield transmission effect), also occurs in 7-heteronorbornanes. A trend is recognized in which the nonequivalence induced by oxygen is rather smaller than that induced by the rear lobe of the N—H bond or by the nitrogen lone pair. It is shown that the Barfield effect also explains the observed nonequivalence between cisoidal H—Cβ—Cγ—H and H—Cγ—Cδ—H couplings in prolines. The calculations also predict similar, though smaller, effects on cisoidal couplings in the tetrahydrofuranyl ring system. Special attention was paid to the practical consequences of the existence of this effect with regard to the pseudorotation analysis of the five-membered sugar ring in nucleic acids. It is found that, in addition to the recently introduced correction for electronegativity and orientation of substituents [Haasnoot, de Leeuw, and Altona, Tetrahedron 36, 2783 (1980)], a cos2 dependency of 3Jcis upon the phase angle of pseudorotation must be taken into account, especially in the case of deoxyribofuranoses.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040320
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  • 160
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    Digitale Medien
    Calculations on the diphenylmethyl anion (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 470-481 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Semiempirical and ab initio calculations for the diphenylmethyl anion and related species are reported. MINDO/3 calculations indicate a coplanar anion with an enlarged bond angle of ∼139° to counteract the steric repulsions. MNDO calculations reveal an expanded bond angle with somewhat greater twist (21°). The ab initio calculations (STO-3G level) reveal an expanded central bond angle with an intermediate degree of phenyl twist. The results are compared with experimental data for this and related anions.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040404
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  • 161
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    Digitale Medien
    A method for the calculation of normal-mode vibrational frequencies using symmetry coordinates. Application to the calculation of secondary deuterium isotope effects on carbocations (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 499-505 
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    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A method is introduced for the calculation of normal-mode vibrational frequencies of polyatomic molecules based on numerical differencing of analytical gradients in symmetry coordinates. This procedure requires a number of gradient evaluations equal to the largest number of symmetry coordinates belonging to any single irreducible representation of the molecular point group (plus a single gradient evaluation at the equilibrium configuration), which is fewer than the 3N-6 (N atoms) gradient evaluations needed for schemes based on Cartesian or internal coordinates. While the proposed method will not generally be as efficient as procedures which involve the direct calculation of energy second derivatives analytically (as are now available for single-determinant wavefunctions) it appears to be equally accurate, and it should be the method of choice for frequency calculations involving multideterminant wavefunctions for which analytical second-derivative algorithms have yet to be developed. The method is illustrated by the calculation of equilibrium secondary deuterium-isotope effects on a number of reactions involving simple carbocations.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040408
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  • 162
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    Digitale Medien
    Ab initio studies of structural features not easily amenable to experiment. 25. Conformational analysis of methyl propanoate and comparison with the methyl ester of glycine (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 494-498 
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    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The molecular geometries of three conformations of methyl propanoate (MEP) (C—C—C=O torsions of 0°, 120°, and 180°) and the potential-energy surfaces of MEP (C—C—C=O torsions) and of the methyl ester of glycine (MEG) (N—C—C=O torsions) have been determined by ab initio gradient calculations at the 4-21G level. MEP has conformational energy minima at 0° and 120° of the C—C—C=O torsion, while the 60-90° range and 180° are energy maxima. For MEG there are two minima (at 0° and 180°) and one barrier to N—C—C=O rotation in the 60-90° range. The N—C—C=O barrier height is about twice as high (4 kcal/mol) as the C—C—C=O barrier. The 180° N—C—C=O minimum is characteristically wide and flat allowing for considerable flexibility of the N—C—C=O torsion in the 150-210° range. This flexibility could be of potential importance for polypeptide systems, since the N—C—C=O angles of helical forms are usually found in this region. The molecular structures of the methyl ester group CH3OC(=O)CHRR′ in several systems are compared and found to be rather constant when R = H and R′ = H, CH3, CH3CH2; or when R = NH2 and R′ = H, CH3, or CH(CH3)2.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040407
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  • 163
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    Digitale Medien
    Ground states of molecules. 64.For part 63, see ref. 1.MNDO Calculations for compounds containing bromine (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 542-551 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: MNDO has been parametrized for bromine. Since d atomic orbitals (AOS) are not included, the calculations are restricted to BrI. Heats of formation, molecular geometries, ionization energies, and dioole moments are reproduced with useful accuracy.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040412
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  • 164
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    Digitale Medien
    Counting of resonance structures for large benzenoid polynuclear hydrocarbons (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 556-562 
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    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A method is presented for counting the number of resonance structures for large benzenoid polynuclear hydrocarbons. Structure counts for even systems are made and compared with those of the odd systems resulting from the removal of one of the π centers from various points in the even structure. A computer program for performing the calculations is also given.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040414
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  • 165
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    Digitale Medien
    Extended basis CNDO calculations of linear and nonlinear electric susceptibilities of some molecular dianions and carbonions using coupled Hartree-Fock perturbation theory (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 578-584 
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    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The results of calculating the average polarizabilities, first and second hyperpolarizabilities and molar Kerr constants of C5H5-, C6H5-, 2-C10H7-, 2-C14H9-, C8H8-2 and C8H6-2 are reported. The main elements of our computational scheme are McWeeny's coupled Hartree-Fock perturbation theory and an extended basis CNDO wave function. It is shown that the studied anions have nonlinearities within the same order of magnitude as their respective uncharged parent molecules. The Kerr constants of these anions are analyzed and the contribution of the various terms is appraised.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040417
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  • 166
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    Digitale Medien
    The 1984 Florida Coast Sanibel symposium Sheraton Palm Coast resort inn, Florida March 1-15, 1984 (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 606-606 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040421
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  • 167
    Digitale Medien
    Digitale Medien
    Molecular orbital theory of the hydrogen bond. XXX. Water-cytosine complexes (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 226-233 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Ab initio SCF and SCF-CI calculations with the STO-3G basis set have been performed to investigate the structures and energies of water-cytosine complexes and the intermolecular water-cytosine surface in the cytosine molecular plane. Although there are six nominal hydrogen-bonding sites in this plane, only three dimers are distinguishable in the ground state. The most stable has an energy of -10.7 kcal/mol, and is found in the N1—H and O2 region. An asymmetric cyclic structure in which the water molecule bridges adjacent N1—H and O2 sites is the preferred form of this dimer. The dimer in the region between O2 and N4—H′ of the amino group is slightly less stable at -10.4 kcal/mol, and also has an asymmetric cyclic structure as the preferred structure, with the water molecule bridging amino N4—H′ and N3 hydrogen-bonding sites. The third dimer has the amino group as the proton donor to water through the hydrogen cis to C5, and a stabilization energy of -7.0 kcal/mol. The water-cytosine surface is characterized by deeper minima and higher barriers than the water-thymine surface and by a decreased mobility of the water molecule between adjacent hydrogen-bonding sites. Absorption of energy by the C2=O group leads to the first n → π* excited state in which interactions of water with O2 are broken. The water-cytosine dimers remain bound in this state, but may change structurally. In the second n → π* state interactions between water and N3 are no longer stabilizing. As a result, the dimer in the O2 and N4—H′ region collapses to either a dimer with water the proton donor to O2, or one with N4—H′ the proton donor to water. The other two dimers remain bound. All excited dimers are destabilized on vertical excitation relative to the ground state.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040213
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  • 168
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    Digitale Medien
    Proton and lithium cation affinities calculated with floating orbital geometry optimization (FOGO) (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 252-259 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The FOGO method is used to calculate proton affinities and lithium cation affinities. The molecules of primary interest in this study are the methyl-substituted amines. In addition, the lithium cation affinity of HF, H2O, CH3OH, H2CO, and HCN are calculated for comparison. Geometries of all species are fully optimized with a double-zeta (DZ) basis set, including polarization on hydrogen and the first-row elements by floating orbitals. Comparison with experimental values demonstrates that structural data and proton affinities resulting from this type of ab initio calculation are of chemical accuracy. The lithium cation affinities are also reasonably well reproduced, but the small experimental differences are not within the accuracy, which can be expected from this type of calculation.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040216
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  • 169
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    Digitale Medien
    Masthead (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983) 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040301
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  • 170
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    Digitale Medien
    Efficient diffuse function-augmented basis sets for anion calculations. III.For parts I and II, and other applications of the 4-31+G basis set, see ref. 1. The 3-21+G basis set for first-row elements, Li-F (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 294-301 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The relatively small diffuse function-augmented basis set, 3-21+G, is shown to describe anion geometries and proton affinities adequately. The diffuse sp orbital exponents are recommended for general use to augment larger basis sets.
    Zusätzliches Material: 8 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040303
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  • 171
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    Digitale Medien
    Multicollinearity and some applications in biological chemistry (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 362-365 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: The relationship between various parameters characterizing a particular system are established using various techniques. In some specific cases, ordinary multiple regression is resorted to for relating one variable to various other variables. However, in such problems there is a high probability of an interrelationship among different variables giving rise to multicollinearity, thereby making it infeasible to place much reliability on ordinary regression techniques. This problem can be circumvented using ridge regression techniques. In this preent investigation an attempt has been made to study the multicollinear problems in biology.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040311
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  • 172
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    Digitale Medien
    Intramolecular interaction effects and the structure of N2OS and N2O2: An Ab initio studyA preliminary account of the work was presented at the Fourth American Conference on Theoretical Chemistry, Boulder, Colorado, June, 1981 (Poster Session F20). (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 379-389 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: An ab initio study of O=N—N=S with full geometry optimization has been carried out to corroborate the presence of an interaction between the terminal atoms in this type of structure, which, in O=N—N=O, apparently stabilizes the cis conformer. Using the unscaled 4-31G basis set with a full set of d functions on the sulfur, there is a potential minimun at the trans but not the cis geometry. A gauche conformer with a torsional angle of 77.2° is the most stable. With N2O2 this basis set gives potential minima at both the cis and trans geometries, but the trans conformer is slightly more stable, contrary to experiment and the results of (7,3) basis-set calculations reported in the literature in which Gaussian lobe functions were employed. Using a (9,5) basis set there is no longer a potential minimum at the cis geometry, and a gauche structure is more stable than the cis conformer as in the case of N2OS with the less-extended basis set. Force constants (harmonic and anharmonic), compliance constants, relaxed force constants, and interaction-displacement coordinates for both molecules are compared for key structural elements.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040313
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  • 173
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    Digitale Medien
    Reaction path calculations for the interaction of the ethylene radical cation with triplet oxygen (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 488-493 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: UMNDO reaction path calculations for trapping of the ethylene-cation radical with ground state oxygen suggest that formation of a dioxetane radical cation proceeds through the intermediacy of a peroxycation radical. The predicted enthalpy of activation (ΔH
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040406
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  • 174
    Digitale Medien
    Digitale Medien
    Guidelines for development of basis sets for the first-order intermolecular interaction energy calculations (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 506-512 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: General guidelines for development of small but efficient basis sets for intermolecular interaction calculations have been proposed and tested for simple model systems. It has been demonstrated that the use of overlap matched atomic orbitals (OMAO) leads to significant improvement in the first-order exchange and electrostatic penetration contributions. Basis sets assuring proper charge distribution lead to a better description of the electrostatic multipole component. The ab-initio effective-core-model potential technique permits a considerable reduction of basis size while having little effect on the selfconsistent field (SCF) interaction energy if basis-set superposition error is corrected properly.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040409
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  • 175
    Digitale Medien
    Digitale Medien
    Determination and characterization of a transition structure for water-formaldehyde addition (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 524-541 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Quantum mechanical calculations of the geometric, energetic, electronic, and vibrational features of a transition structure for gas-phase water-formaldehyde addition (FW1
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040411
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  • 176
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    Digitale Medien
    Orbital relaxation in the Rydberg series of the lithium atom. An excited state SCF calculation (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 563-566 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: Self-consistent-field (SCF) calculations for a series of Rydberg states (1s2ns)2S of the Li atom are performed using the generalized Brillouin theorem (GBT) method. The calculated energy is a proper upper bound to the excited state energy. The SCF term values of the Rydberg states are almost the same as those of the frozen-core approximation ones. The orbital behavior shows that the core is slightly expanded by the penetration of the Rydberg orbitals, and the higher Rydberg orbitals can be very well represented by the modified hydrogen-like orbitals.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040415
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  • 177
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    Digitale Medien
    Operator technique for obtaining the recursion formulas of characteristic and matching polynomials as applied to polyhex graphs (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 585-593 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: A simple and efficient method, called an operator technique, for obtaining the recurrence relation of a given counting polynomial, e.g., characteristic PG(x) or matching MG(x) polynomial, for periodic networks is proposed. By using this technique the recurrence relations of the PG(x) and MG(x) polynomials for the linear zigzag-type and kinked polyacene graphs were obtained. For the lower members of these series of graphs, the coefficients of PG(x) and MG(x) polynomials are tabulated.
    Zusätzliches Material: 6 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540040418
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  • 178
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    Digitale Medien
    Kinetic study of the reactions of CL and BR with H2O2 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 1311-1319 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reactions of Cl and Br atoms with H2O2 have been studied in the range of 300-350 K using the very-low-pressure-reactor technique. It was found that metathesis to produce HX and HO2 is the only significant process (≤99%). For the reaction of Br \documentclass{article}\pagestyle{empty}\begin{document}$${\rm Br}+{\rm H}_2{\rm O}_2\buildrel{2}\over{\rightarrow}{\rm Hbr} + {\rm HO}_2$$\end{document} k2 (300 K) = 1.3 ± 0.45 × 10-14 and k2 (350 K) = 3.75 ± 1.1 × 10-14 cm3/molecules·s, with an activation energy of 4.6 ± 0.7 kcal/mol. Using an estimated A factor for A2, we find \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{l} k_2 ({\rm benttransitionstate}) = 1.6 \times 10^{ - 11 - 4.3/\theta } \\ k_2 ({\rm lineartransitionstate}) = 4 \times 10^{ - 12 - 3.5/\theta } \\ \end{array}$$\end{document} suggesting that a best choice is E2 = 3.9 ± 0.4 kcal/mol. The relation of these values to ΔHf0 (HO2) is discussed.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550151206
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  • 179
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    Digitale Medien
    The kinetics of the reactions of i-C3F7 radicals with BR2 and HBr (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 1329-1334 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reactions \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{l} (2)i - {\rm C}_3 {\rm H}_7 + {\rm Br}_2 \to i - {\rm C}_3 {\rm F}_7 {\rm Br} + {\rm Br} \\ (3)i - {\rm C}_3 {\rm H}_7 + {\rm HBr}_2 \to i - {\rm C}_3 {\rm F}_7 {\rm H} + {\rm Br} \\ \end{array}$$\end{document} have been studied competitively in the vapor phase over the range of 52-204°C. The i-C3F7 radicals were generated by means of the reaction \documentclass{article}\pagestyle{empty}\begin{document}$${\rm Br} + i - {\rm C}_3 {\rm F}_7 {\rm I} \to {\rm IBr} + i - {\rm C}_3 {\rm F}_7 $$\end{document} It was found that \documentclass{article}\pagestyle{empty}\begin{document}$${\rm log} k({\rm s}^{ - 1}) = (15.74 \pm .022) - (45,660 \pm 526)/4.576T $$\end{document} where θ = 2.303RT J/mol. Absolute Arrhenius parameters are derived for the reactions \documentclass{article}\pagestyle{empty}\begin{document}$${\rm R} + {\rm HBr} \to {\rm RH} + {\rm Br}$$\end{document} where R = CF3, C2F5, and i-C3F7.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550151208
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  • 180
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    Digitale Medien
    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983) 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150101
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  • 181
    Digitale Medien
    Digitale Medien
    Mechanism of acetylene-chlorine mixture explosion initiated by small additions of oxygen (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 1-4 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An improved radical-chain scheme of acetylene-chlorine mixture explosion initiated by small additions of oxygen is proposed. It includes among others the three-body formation of chemically activated state (2) and describes the inhibiting effect of oxygen below the explosion limit.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150102
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  • 182
    Digitale Medien
    Digitale Medien
    Kinetics of the reactions of O3 and OH radicals with furan and thiophene at 298 ± 2 K (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 51-61 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Rate constants for the reactions of O3 and OH radicals with furan and thiophene have been determined at 298 ± 2 K. The rate constants obtained for the O3 reactions were (2.42 ± 0.28) × 10-18 cm3/molec·s for furan and 〈6 ×10-20 cm3/molec·s for thiophene. The rate constants for the OH radical reactions, relative to a rate constant for the reaction of OH radicals with n-hexane of (5.70 ± 0.09) × 10-12 cm3/molec·s, were determined to be (4.01 ± 0.30) × 10-11 cm3/molec·s for furan and (9.58 ± 0.38) × 10-12 cm3/molec·s for thiophene. There are to date no reported rate constant data for the reactions of OH radicals with furan and thiophene or for the reaction of O3 with furan. The data are compared and discussed with respect to those for other alkenes, dialkenes, and heteroatom containing organics.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150106
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  • 183
    Digitale Medien
    Digitale Medien
    Pyrolysis studies of main group metal-alkyl bond dissociation energies: VLPP of GeMe4, SbEt3, PbEt4, and PEt3 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 167-185 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The bond dissociation energies of tetramethyl germane, triethyl stibine, tetraethyl lead, and triethylphosphine were determined using the technique of very-low-pressure pyrolysis. Arguments are presented for log A ≥ 17.0. The respective dissociation energies ΔH298 are 83, 57, 54, and 68 (±2) kcal/mol. A consistent set of methyl bond energies to main group metals is determined from these and previous results, and is examined for trends. Bond energies for various radicals to tin are also derived.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150207
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  • 184
    Digitale Medien
    Digitale Medien
    Relative rate constants for removal of vibrationally excited OH(X2πi)v=9 by some small molecules at room temperature (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 151-165 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Vibrationally excited OH in v = 9 [designated OH†(9)] was generated by the reaction of hydrogen atoms with ozone in a fast-flow discharge system at 300 ± 3 K and a total pressure of 1.1 ± 0.1 torr, with argon as the carrier gas. The addition of a species X, which can deactivate the OH†(9) or react with it, led to a decrease in the Meinel band chemiluminescent emission intensities at both 626 nm (9 → 3 band) and 519 nm (9 → 2 band), which were monitored as a function of the concentration of X. Application of the kinetic scheme developed previously for this chemical system gave the relative rate constant for the removal of OH†(9) by X. The relative rate constants determined in this study, taking O2 as the reference deactivator (kO2 = 1.0), are as follows: He ≤ 0.02; H2 ≤ 0.05; SF6 0.09 ± 0.01; CF4 0.19 ± 0.01; N2O 3.5 ± 0.4; NO 17.7 ± 1.5; H2O 74.3 ± 2.9; D2O 57.6 ± 2.0; NH3 61.3 ± 1.9; ND3 58.7 ± 1.6; SO2 7.1 ± 1.4; COS 8.4 ± 1.7; H2S 33.7 ± 8.4; CH4 1.56 ± 0.03; CD4 1.06 ± 0.06. Application of these relative rate constants to conditions in the upper atmosphere (60-100 km) suggests that OH†(9) is removed primarily by deactivation by O2, and at altitudes ≳90 km, possibly by O(3P). However, since O2 is unusually efficient for a homonuclear diatomic in deactivating OH†(9), it may not be the primary deactivator for the lower (v ≤ 8) vibrational levels. These results are compared to earlier studies of OH†(9), and possible mechanisms of interaction of OH†(9) with these molecules are discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150206
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  • 185
    Digitale Medien
    Digitale Medien
    Reaction of pentafluoroethyl radicals with hydrogen cyanide (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 187-196 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of C2F5 radicals with HCN has been studied over the range of 533-673 K using the pyrolysis of pentafluoroethyl iodide as the free-radical source. Arrhenius parameters for the reaction relative to C4F10 recombination are given by \documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{\rm H} /k_{c^{1/2} } = (5.36 \pm 0.15) - (57.3 \pm 1.8)/\theta $$\end{document} where θ = 2.303RT kJ/mol and kH/kc1/2 is in cm3/2/mol1/2·s1/2.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150208
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  • 186
    Digitale Medien
    Digitale Medien
    Intramolecular hydrogen isotope effect in the pyrolysis of diethyl carbonate-1,1,1,2,2-d5 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 461-468 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The thermal unimolecular decomposition of diethyl carbonate-1,1,1,2,2-d5 has been examined in the high-pressure-limiting region. The observed chemistry is consistent with a simple, competitive two-channel model: The intramolecular isotope effect kH/kD has been determined, and the relative Arrhenius parameters for the two channels are given by \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{\rm H} /k_D = (0.80 \pm 0.18)\,\exp [(1140 \pm 260){\rm cal/mol/RT}] $$\end{document} over the temperature range of 540-620 K. These Arrhenius parameters predict an isotope effect kH/kD = 5.4 at 300 K.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150506
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  • 187
    Digitale Medien
    Digitale Medien
    The use of transition-state theory to extrapolate rate coefficients for reactions of OH with alkanes (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 503-504 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150509
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  • 188
    Digitale Medien
    Digitale Medien
    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983) 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150601
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  • 189
    Digitale Medien
    Digitale Medien
    Rate of formation of toluene from ethylbenzene (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 469-474 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The rate of formation of toluene from ethylbenzene was studied at atmospheric pressure in the temperature range of 600-725°C in conventional flow equipment. Residence times were 0.55-1.7 s, and initial partial pressures of ethylbenzene (H2O diluent) were 0.05-0.17 atm. The rate of appearance of toluene measures [1] the rate of the reaction C6H5C2H5 → C6H5CH3· + CH3·, with log k = 15.70 - 74.49 ± 3.2/θ. From the activation energy, E0 for the decomposition is estimated to be 72.2 ± 3.2 kcal/mol. The results are compatible with those of Esteban et al. [2], for which regression analysis gives log k1 = 14.79 - 70.76/θ. A composite, log k = 15.10 - 72.0/θ, fits both sets of data and is experimentally indistinguishable from Robaugh and Steina's [3] recent estimate by the VLPP technique or other estimates in the literature [4-6]. In light of the high overall conversion of ethylbenzene studied (2-80%), the industrial-type flow equipment, and the widely differing methods of characterization and analysis, the excellent agreement with the results of [2,3,5] is worthy of note. The data are compatible with current estimates of the heat of formation of benzyl radicals [6,7].
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150507
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  • 190
    Digitale Medien
    Digitale Medien
    The thermal decomposition of n-hexane (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 475-502 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the pyrolysis of n-hexane was studied in a conventional static reactor over a temperature range of 650-840 K. The overall reaction is essentially first order with the kinetic parameters A = 1013.92 s-1 and EA = 260.3 kJ/mol. The distributions of the main products were analyzed by gas chromatography. A reaction model involving 240 elementary reactions was developed to describe the experimental rate data. The agreement of the model with experimental data was surprisingly good over a wide range of temperatures and pressures and up to medium extents of conversion. Methods for sensitivity studies based upon the quasi-stationary-state assumption (QSSA) were developed, and for a number of more detailed effects, such as self-inhibition, explanations could be given. It was also shown that the hexyl isomerization reactions influence strongly the product distribution. The outstanding capability of kinetic modeling with computer simulations in handling complex kinetic systems is demonstrated.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150508
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  • 191
    Digitale Medien
    Digitale Medien
    Kinetics of gas-phase decomposition of oxetan and oxetan-2,2-d2 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 505-519 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The pressure dependence of the first-order rate coefficient of oxetan and oxetan-2,2-d2 decomposition has been studied in the pressure range from about 7 kPa down to 0.01 kPa at various temperatures between 673 and 758 K. Experimental data were analyzed using RRKM theory. Interpretation of the fall-off curves lends support to the high-pressure Arrhenius parameters A = 1015.42s-1 and EA = 259.5 kJ/mol derived from measurements made in the pressure-independent range. Decomposition of oxetan is found to occur via biradical intermediates. Data for the kinetic isotope effect were used to derive kinetic parameters for the ring-opening elementary steps in oxetan and oxetan-d2 decomposition.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150602
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  • 192
    Digitale Medien
    Digitale Medien
    The kinetics of secondary reactions in the iodination of monogermane. The effect of iodine substitution on the Ge—H bond dissociation energy (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 561-568 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A study has been made both of secondary reactions occurring during the reaction of I2 with GeH4, and of the direct reaction between I2 and GeH3I. Both these studies show that the abstraction reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm I}^ \cdot + {\rm GeH}_{\rm 3} {\rm I} \to {\rm \dot GeH}_{\rm 2} {\rm I + HI} $$\end{document} occurs about 30 times faster than the reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm I}^ \cdot + {\rm GeH}_{\rm 4} \to {\rm \dot GeH}_{\rm 3} {\rm + HI} $$\end{document} in the temperature range of 425-446 K. This information is used to show that iodine substitution weakens Ge-H bonds by 14.4 ± 2.5 kJ/mol and that D(H2IGe—H) = 332 ± 10 kJ/mol (79.3 kcal/mol). Possible reasons for the effects of halogen substituents on Ge—H and Si—H bond strengths are discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150606
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  • 193
    Digitale Medien
    Digitale Medien
    Masthead (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983) 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150701
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  • 194
    Digitale Medien
    Digitale Medien
    Rate constants for the gas-phase reactions of OH radicals with β-dimethylstyrene and acetone. Mechanism of ββdimethylstyrene NOx - air photooxidation (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 579-586 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The rate constants of gas-phase reactions of the hydroxyl radical with β-dimethylstyrene and acetone have been determined by a relative method at 298 K. The values obtained are β-dimethylstyrene (3.3 ± 0.5) × 10-11 cm3/molecule·s and acetone (6.6 ± 0.9) × 10-13 cm3/molecule·s. A simplified kinetic treatment of the experimental data shows that β-dimethylstyrene is stoichiometrically converted to benzaldehyde and acetone. In the photooxidation study of benzaldehyde, carbon dioxide was the only detected product. The ratio between carbon dioxide produced and benzaldehyde reacted was ≥1.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150608
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  • 195
    Digitale Medien
    Digitale Medien
    Kinetics of the gas-phase reaction CH3F + I2 ⇆ CH2FI + HI: The C—H bond dissociation energy in methyl and methylene fluorides (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 569-577 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the gas-phase reaction of CH3F with I2 have been studied spectrophotometrically from 629 to 710 K, and were determined to be consistent with the following mechanism: A least-squares analysis of the kinetic data taken in the initial stages of reaction resulted in \documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_4 (M^{ - 1} \cdot s^{ - 1}) = (11.3 \pm 0.1) - (30.8 \pm 0.2)/\theta $$\end{document} where θ = 4.575T/1000 kcal/mol. The errors represent one standard deviation. The experimental activation energy E4 = 30.8 ± 0.2 kcal/mol was combined with the assumption E3 = 1 ± 1 kcal/mol and estimated heat capacities to obtain \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta H_r^\circ (4,g,298K) = 30.0 \pm 1{\rm kcal}/{\rm mol} $$\end{document} The enthalpy change at 298 K was combined with selected thermochemical data to derive \documentclass{article}\pagestyle{empty}\begin{document}$$ DH^\circ ({\rm CH}_{\rm 2} {\rm F} - {\rm H}) = 101.2 \pm 1{\rm kcal/mol} $$\end{document} The kinetic studies of ĊHF2 and CH2F2 have been reevaluated to yield \documentclass{article}\pagestyle{empty}\begin{document}$$ DH^ \circ \left( {{\rm CHF}_{\rm 2} - {\rm H}} \right) = 103.2 \pm 1\,{{{\rm kcal}} \mathord{\left/ {\vphantom {{{\rm kcal}} {{\rm mol}}}} \right. \kern-\nulldelimiterspace} {{\rm mol}}} $$\end{document} These results are combined with literature data to yield the C—H, C—F, and C—Cl bond dissociation energies in their respective fluoromethanes, and the effect of α-fluorine substitution is discussed.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150607
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  • 196
    Digitale Medien
    Digitale Medien
    TI(III) oxidation of alkenes and alkynes and Ru(III) catalysis in the oxidation of alkenes: A kinetic and mechanistic study (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 587-602 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The oxidation of trans-stilbene, phenylacetylene, and diphenylacetylene by Tl(OAc)3 in aqueous acetic acid medium in the presence of HClO4 follows the rate law \documentclass{article}\pagestyle{empty}\begin{document}$$ -\frac{{d[{\rm TI(OAc})_3]}}{{dt}} = k_2 [{\rm substrate}][{\rm TI(OAc}_3)]H_0 $$\end{document} in [H+] of 0.1-1.0M, the [H+] dependence below 0.1M being marginal. The reactions are strongly dielectric dependent. The order of reactivity among the substrates is styrene 〉 phenylacetylene and trans-stilbene 〉 diphenylacetylene. A mechanism involving the oxythallation adduct by the Tl+(OAc)2 species has been discussed. The use of Ru(III) as a homogeneous catalyst brings a change in the kinetic orders for trans-stilbene, the rate law being \documentclass{article}\pagestyle{empty}\begin{document}$$ -\frac{{d[{\rm TI(OAc})_3]}}{{dt}} = \frac{{kK[{\rm substrate}][{\rm Ru(III})][{\rm TI(OAc})_3]^\circ }}{{1 + K[{\rm substrate}]}} $$\end{document} The formation constants K for the Ru(III)-alkene π complex at 40, 50, and 60°C are 90.14M-1, 105.2M-1, and 127.7M-1, respectively. Interestingly the oxidation of phenylacetylene and diphenylacetylene does not undergo catalysis by Ru(III). The mechanism involving the metal-arene π complex is discussed.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150609
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  • 197
    Digitale Medien
    Digitale Medien
    A reexamination of the pyrolysis of bis trifluoromethyl peroxide. Addendum: Concerning D(CF3O2-CF3) and D(CF3-O2) (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 605-607 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Earlier arguments concerning D(CF3O2-CF3) and D(CF3-O2) are shown to be probably wrong. New values of 86 and 49 kcal/mol, respectively, are derived. C-O bond strengths are compared between CF3- and CH3-containing compounds.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150702
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  • 198
    Digitale Medien
    Digitale Medien
    Induced heterogeneity, a novel technique for the study of gas-phase reactions. 2. Direct study of C—C bond scission in ethane (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 845-853 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Deliberate activation of the reaction vessel surface leads to the domination of chain termination in ethane pyrolysis by the reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ (5) {\rm H} \to \frac{1}{2}{\rm H}_2 $$\end{document}As a result, chains are dramatically reduced in length, methane yields are entirely primary and larger in proportion to other products, and values of k1 \documentclass{article}\pagestyle{empty}\begin{document}$$ (1){\rm C}_2 {\rm H}_6 \to 2{\rm CH}_3 $$\end{document} can be directly determined from methane yield data without ambiguity. Experiments carried out in the temperature range of 841-913K at initial ethane pressures of 1-20 torr, without and with added nitrogen, yield the infinite pressure Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}k_{\rm 1} ({\rm s}^{ - 1}) = 16.52 \pm 0.44 - 87900 \pm 1760{\rm cal}/{\rm mol}/2.303RT $$\end{document}It is shown that most previously published data can be combined with those of this study to yield \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}k_{\rm 1} ({\rm s}^{ - 1}) = 16.63 \pm 0.18 - 88400 \pm 720{\rm cal}/{\rm mol}/2.303RT $$\end{document}Fall-off curves for k1 as a function of pressure are in good agreement with those from other laboratories. From these the relevant data for k-1 can be extracted for use in other kinetic studies.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150813
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  • 199
    Digitale Medien
    Digitale Medien
    Sensitivity analysis in chemical kinetics by the method of polynomial approximations (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 959-987 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new approach, the method of polynomial approximations (PAM), to the sensitivity analysis in chemical kinetics is presented. The method is based on first dividing the time domain of interest into subintervals, and then, within each subinterval, using low-degree interpolation polynomials to mimic the system temporal behavior. This procedure forces all parametric dependences of the system to reside in the expansion coefficients and transforms the differential sensitivity equations into a set of algebraic ones. The major computational effort of PAM is proportional to the number of components in the system, not to the number of parameters. In addition, higher order sensitivity coefficients in PAM can be generated quite readily once first-order ones are known. The information required to divide the time domain comes from a preliminary simulation study of the system temporal behavior, which is always available in any kind of modeling studies. Typically, for an interpolation polynomial of degree 3-4, only 10-20 subintervals are needed to attain satisfactory accuracy. The application of PAM is well suited to large-scale kinetic models, especially when an inexpensive scanning of the system sensitivity behavior is desired. The extremely high computational speed of PAM in securing sensitivity informations was demonstrated by two illustrative kinetic examples. Furthermore the problem of utilizing sensitivity information to unravel the functional dependence of a species concentration upon rate coefficients, to simplify a complex reaction model, and to elucidate mechanistic details of a reaction process was examined in detail.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550151003
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  • 200
    Digitale Medien
    Digitale Medien
    Glycosaminoglycans (GASs) in human cerebral tumors (1982)
    Springer
    Acta neuropathologica 58 (1982), S. 115-119 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Biochemistry ; Cerebral tumours ; Electrophoresis ; Glycosaminoglycans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary GAG electrophoretic pattern and concentration have been studied in 38 human cerebral tumors and in specimens of normal nervous tissue. Gray matter had higher total GAG concentration and higher CA to HA ratio than white matter. In both, DS was present in very small amount whereas HS represented 15% of GAGs. All benign gliomas displayed the same electrophoretic pattern and contained more GAGs than normal nervous tissue. Dermatan sulfate was detected in malignant gliomas, as well as in other oncotypes, due to their mesodermic component. Ependymomas were particularly rich in HS and meningiomas were poor in HA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00691651
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