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  • 101
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 51-61 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have carried out a kinetic study of the 4-pyridinecarboxaldehyde plus n-hexylamine system, at 25°C, in water-dioxan mixtures (0-60% v/v) and in the pH range pKa + 1.5 〉 pH 〉 pKa - 1.5, where pKa is the pK value of the conjugate acid of the amine. The results obtained could be interpreted in terms of a rate constant for Schiff's base hydrolysis and a rate constant for the reaction between the nonprotonated n-hexylamine and the nonhydrated form of 4-pyridinecarboxaldehyde. Both constants decrease sharply as the dioxan content of the solvent increases, in a manner consistent with Marshall's model [J. Phys. Chem., 74, 346 (1970)]. It is suggested that the transition state of the rate-limiting step (carbinolamine dehydration) is highly solvated by water molecules and has a high separation of charges.
    Additional Material: 5 Ill.
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  • 102
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 31-50 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of oxidation of thiosemicarbazide (TSC) and its hydrazone (Benzaldehyde thiosemicarbazone) by chloramine-T (CAT) and dichloramine-T (DCT) in aqueous methanol medium in the presence of perchloric acid has been studied. Oxidation of TSC by both the oxidants showed first order dependences in [oxidant], fractional order in [TSC] and nearly inverse first order in [H+]. The conversion of TSC into its benzaldehyde hydrazone changed the rate dependence in [CAT] from first to second order, while the dependence in [DCT] remained unchanged. The dependence in [TSC] changes from fractional order to zero order in both CAT and DCT oxidations. The rate followed inverse fractional order kinetics in [H+] in both the cases. Increase in ionic strength of the medium slightly decreased the rate, while the decrease in dielectric constant of the medium increased the rates of oxidations for both the oxidants. But the addition of reaction products, p-toluenesulphonamide and chloride had no effect on the rate. Oxidation of TSC with both the oxidants has been shown to follow Michaelis-Menten type mechanism. In hydrazone oxidations oxidants have been shown to disproportionate in slow steps to HOCl, which in turn attacks the substrate in fast steps to give the final products. [TSC] was varied at different temperatures and the constants of rate limiting steps were calculated at each temperature. Using the latter constants the activation parameters have been computed from the Arrhenius plots. The rate constants have been predicted from the rate law for the variation of [H+] at constant [TSC] and [oxidant]. The predicted values are in reasonable agreement with the experimental rate constants, providing additional support to the suggested mechanisms.
    Additional Material: 5 Ill.
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  • 103
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 83-99 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the elementary sensitivity densities, a reaction rate sensitivity gradient is obtained which is the derivative of the rate of species concentration change with respect to the rate coefficient. The dimensionless (log-normalized) form of the reaction rate sensitivity gradient is the ratio of the rate of concentration change of species i due to elementary reaction j and the net rate of concentration change of species i. This result provides a mathematical basis for the use of various forms of reaction rate analyses in the study of complex reaction mechanisms. The kinetic information inherent in the relative reaction rate matrix is extracted by principal component analysis. The method is used to analyze the mechanism of high-temperature formaldehyde oxidation and high-temperature propane pyrolysis. Ranking of the elementary reactions allowed us to reduce significantly the original mechanisms and a detailed study of the results revealed the reaction structures and the major reaction paths of the species.
    Additional Material: 6 Tab.
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  • 104
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 165-174 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The canonical formalism of the statistical adiabatic channel model is used to calculate limiting high pressure rate constants for the H + CH3 → CH4 recombination reaction on a recently reported analytic potential energy surface based on ab initio calculations. An effective adiabatic channel potential which incorporates the Gφφ matrix element of the twofold degenerate H3C—H transitional bending mode, quartic anharmonicity, and state selected mode coupling effects is implemented. The rate constants calculated over the temperature range 200-1000 K are in very good agreement with recent canonical variational transition state theory calculations performed on the same surface. The comparison with experimental results is also discussed.
    Additional Material: 2 Ill.
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  • 105
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 193-206 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolysis kinetics of the title compounds has been studied in a stirred-flow reactor over the temperature range 440-530°C and pressures between 5 and 14 torr. Benzyl t-butyl sulfide and phenyl t-butyl ether formed isobutene as product in over 98% yield, together with the corresponding benzyl thiol and phenol. The benzyl thiol decomposes to a large extent into hydrogen sulfide and bibenzyl. In the pyrolysis of phenyl t-butyl sulfide, the hydrocarbon products consisted of 80 ±5% isobutene plus 20% isobutane, while the sulfur containing products were thiophenol and diphenyl disulfide. Order one kinetics was observed for the consumption of the reactants. The first order rate coefficients, based on isobutene production, followed the Arrhenius equations: Benzyl t-butyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$k(s^{ - 1}) = 10^{13.82 \pm 0.41} \exp ( - 214 \pm 6{\rm kJ/mol }RT)$$\end{document} Phenyl t-butyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$k(s^{ - 1}) = 10^{12.03 \pm 0.39} \exp ( - 188 \pm 6{\rm kJ/mol }RT)$$\end{document} Phenyl t-butyl ether: \documentclass{article}\pagestyle{empty}\begin{document}$$k(s^{ - 1}) = 10^{14.30 \pm 0.21} \exp ( - 211 \pm 3{\rm kJ/mol }RT)$$\end{document}For benzyl t-butyl sulfide and phenyl t-butyl ether, the results suggest a unimolecular mechanism involving polar four center cyclic transition states. For phenyl t-butyl sulfide, the t-butyl-sulfur single bond fission mechanism is a parallel, less important process than the complex fission one.
    Additional Material: 2 Ill.
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  • 106
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 107
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 331-341 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following reactions: were studied over the temperature ranges 533-687 K, 563-663 K, and 503-613 K for the forward reactions respectively and over 683-763 K, for the back reaction. Arrhenius parameters for chlorine atom transfer were determined relative to the combination of the attacking radicals. The ΔHr°(1) = -3.95 ± 0.45 kcal mol-1 was calculated and from this value the ΔH∮(C2F5Cl) = -2.66.3 ± 2.5 kcal mol-1 and D(C2F5-Cl) = 82.0 ± 1.2 kcal mol-1 were obtained. Besides, the ΔHr°(2) was estimated leading to D(CF2ClCF2Cl) = 79.2 ± 5 Kcal mol-1. The bond dissociation energies and the heat of formation are compared with those of the literature. The effect of the halogen substitutents as well as the importance of the polar effects for halogen transfer processes are discussed.
    Additional Material: 1 Ill.
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  • 108
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 109
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 375-386 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetic studies of the transfer of hydrogen from 9,10-dihydrophenanthrene to anthracene were done at 350°C in the liquid phase. Principal products were phenanthrene and 9,10-dihydroanthracene. Autocatalysis occurred at low extents of reaction, where H-transfer from 9,10-dihydroanthracene to anthracene caused an increase in free radical concentrations. At higher extents of reaction, 9,10-dihydroanthracene inhibited rates by diverting intermediate 9-hydrophenanthryl radicals back to reactants. A quantitative kinetic model based on literature rate and thermodynamic data fits the observations well. A key net reaction is the transfer of an H-atom from a radical (9-hydrophenanthryl) to a molecule (anthracene). It is shown that this process does not involve a free H-atom intermediate. The derived rate constant for this exothermic process (7.5 × 103 M-1 s-1) is considerably greater than that for the related, but thermoneutral H-transfer between anthracene moieties (120 M-1 s-1).
    Additional Material: 2 Ill.
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  • 110
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 431-437 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rates of reaction for the alkaline hydrolysis of various hydroxamic acids in the presence of cetyltrimethylammonium bromide have been determined. Empirical reaction orders of zero, one-half, and one were found for the hydroxamic acids depending upon reaction conditions and substrate structure. N-methylhydroxamic acids exhibited only first-order kinetics. The results are consistent with the Michaelis-Menten rate equation.
    Additional Material: 4 Tab.
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  • 111
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 465-476 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrogallol (1,2.3-benzentriol, 1) reacts with dioxygen in weakly alkaline solutions to form purpurogallin (2,3,4,6-tetrahydroxy-5H-benzocycloheptene-5-one, 2) which then reacts to form purpurogalloquinone (3) which then decays to a product absorbing at 440 nm. The formation of 3 requires 1.5 mol O2 per mol 1, and 1.0 mol per mol 2. No O2 is consumed during the decay of 3, and this reaction, being insensitive to O2 concentrations and the presence of both superoxide dismutase (SOD) and catalase, does not appear to be an oxidation. The first-order rate of decay of 3 decreases with increasing pH. 1 and 3 react at pH 9.0 with a second-order rate constant of ca. 100 M-1 s-1. SOD inhibits the oxidation of 1 and 2. Slight and variable apparent inhibition of the oxidation of 2 and 3 by SOD may be due to trace impurities in 2, but not contamination by 1. The peak concentration of 3 is attained more rapidly during the oxidation of 1 than during the oxidation of 2. A kinetic scheme based on parallel oxidation of 1 by dioxygen and superoxide, and it which the semiquinone of 1 oxidizes 2, is partially successful in simulating the observed kinetic behavior.
    Additional Material: 7 Ill.
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  • 112
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 485-498 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of the hydroxyl radical, OH, with several reactants have been studied near 1200 K in shock tube experiments in which UV absorption was used to monitor the OH concentration. The values of the rate coefficients were found to be 2.7 × 1012, 2.6 × 1012, 2.8 × 1013, and 1.26 × 1013 cm3/mol-s for the reactions of OH with hydrogen, methane, cyclopentane, and isobutane, respectively. These measured values are compared with previous experimental results and transition-state theory calculations.
    Additional Material: 5 Ill.
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  • 113
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 535-546 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The near U-V photolysis of t-butyl nitrite has been studied over the temperature range 303-393 K. Under these conditions t-butyl nitrite was shown to be a very clean photochemical source of t-butoxy radicals. This allows a study of the decomposition of the t-butoxy radical to be made over this temperature range (3). Extrapolation of the rate constants k3 to high pressure and combination with our previous thermal data give the results: \documentclass{article}\pagestyle{empty}\begin{document}$$k_3 (\infty)/{\rm s}^{{\rm - 1}} = 10^{14.04 \pm 0.37} \exp (- 7519 \pm 70.5/T)$$\end{document}
    Additional Material: 5 Ill.
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  • 114
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 575-591 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title reaction has been studied in a static quartz reaction vessel between 587 and 658 K at pressures between 40 and 152 torr. The dehydrochlorination is the only significant reaction and is autoaccelerated by the produced HCl. Numerical modelling indicates that the Rice-Herzfeld mechanism, generally used for describing the pyrolysis of halogenated ethanes, has to be completed in the case of CC13CH3 with additional transfer reactions converting “dead” radicals into chain carriers and vice-versa. The numerical simulation fits the experimental results, in the absence as well as in the presence of different amounts of added HCl. The dehydrochlorination is also accelerated by the addition of CCl4, which can be explained in terms of additional elementary steps involving · CCl3 radicals.
    Additional Material: 9 Ill.
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  • 115
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 643-666 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Propyne (p-C3H4) or allene (a-C3H4) mixtures, highly diluted with Ar, were heated to the temperature range 1200-1570 K at pressures of 1.7-2.6 atm behind reflected shock waves. The thermal decompositions of propyne and allene were studied by both measuring the profiles of the IR emission at 3.48 μm or 5.18 μm and analyzing the concentrations of reacted gas mixtures. The mechanism and the rate constant expressions were discussed from both the profiles and the concentrations of reactant and products obtained. The rate constant expressions for reactions, (1) p-C3H4 → a-C3H4, (-1) a-C3H4 → p-C3H4, and (5) p-C3H4 + H → CH3 + C2H2 were evaluated.
    Additional Material: 14 Ill.
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  • 116
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 621-633 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of oxidation of thiocyanate ion (NCS-) by iodine monochloride and iodine has been studied in aqueous perchloric acid medium. The rates of oxidations followed the rate laws: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {- \frac{{d[{\rm ICl]}}}{{dt}} = \frac{{k[{\rm ICl][NCS}^ -][{\rm H}^ +]}}{{l + {\rm K[NCS}^ -][{\rm H}^ +]}}} \\ {- \frac{{d[{\rm I}_{\rm 2}]}}{{dt}} = \frac{{k'[{\rm I}_{\rm 3} ^ -][{\rm NCS}^ -][{\rm H}^ +]}}{{[{\rm I}^ -][1 + {\rm K'[H}^ +]]}}{\rm at low [H}^ +]} \\ {{\rm and} - \frac{{d[{\rm I}_{\rm 2}]}}{{dt}} = \frac{{k''[{\rm I}_{\rm 2}]}}{{k'' + [{\rm H}^ +][{\rm I}^ -]}}{\rm at high [H}^ +]} \\ \end{array} $$\end{document} Variations in ionic strength and dielectric constant of the medium had little effects on the rates of reactions with both the oxidants. Mechanisms consistent with the observed rate laws have been suggested. Rate limiting steps have been identified and the constants of some of these steps have been evaluated by varying [NCS-] at each temperature. Activation parameters were computed from the Arrhenius plots. The rate constants predicted from the rate law as [NCS-], and [H+], varied in iodine monochloride oxidation, are in good agreement with the experimental values providing support to the proposed mechanism.
    Additional Material: 2 Ill.
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  • 117
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 689-701 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of propane was studied behind reflected shock waves over the temperature range 1100-1450 K and the pressure range 1.5-2.6 atm, by both monitoring the time variations of absorption at 3.39 μm and analyzing the concentrations of the reacted gas mixtures. The rate constants of the elementary reactions were discussed from the results. The rate constant expressions, k1 = 1.1 × 1016 exp (-84 kcal/RT) s-1 and k4 = 9.3 × 1013 exp(-8 kcal/RT) cm3 mol-1 s-1, of reactions C3H8 → CH3 + C2H5 and C3H8 + H → n-C3H7 + H2 were evaluated, respectively.
    Additional Material: 7 Ill.
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  • 118
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 715-727 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The UV absorption spectrum and the kinetics of the self combination reaction of the CCl3 radical were studied by flash photolysis in the temperature range 253-623 K. Experiments were performed at the atmospheric pressure, except for a few runs at the highest temperatures, which were performed between 30 and 760 torr. CCl3 radicals were generated by flash photolysis of molecular chlorine in the presence of chloroform. The UV spectrum exhibits a strong unstructured band between 195 and 260 nm with a maximum at 211 ± 2 nm. The absorption cross section, measured relative to σ(HO2), is σ(CCl3) = (1.45 ± 0.35) × 10-17 cm2 molecule-1 at the maximum. This value takes into account the uncertainty in σ(HO2) which was taken equal to (4.9 ± 0.7) × 10-18 cm2 molecule-1. The absolute rate constant for the CCl3 mutual combination was determined by computer simulation of the transient decays. The rate constant, which exhibits a slight negative temperature coefficient, can be expressed as: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_6 = (3.3 \pm 0.8) \times 10^{- 12} (T/298)^{- 1.0 \pm 0.2} {\rm cm}^{\rm 3} {\rm molecule}^{- 1} {\rm s}^{- 1} {\rm at 760 torr}{\rm.} $$\end{document}The study of the pressure dependence showed that only a slight fall-off behavior could be observed at the highest temperature (623 K). This result was corroborated by RRKM calculations which showed that the rate constant is at the high pressure limit under most experimental conditions below 600 K.
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  • 119
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the solvolytic aquation of cis-(Bromo) (imidazole) bis(ethylenediamine) cobalt (III) and cis-(Bromo) (N-methylimidazole) bis(ethylenediamine) cobalt(III) have been investigated in aqueous methanol media with methanol content 0-80% by weight and at temperatures 40-55°C. The pseudo-first order rate constant decreases with increasing methanol content. Plots of log kaqs vs. Ds-1 (where Ds is the bulk-dielectric constant of the solvent mixture) and log kaqs vs. the Grunwald-Winstein Y-solvent parameter are nonlinear, the curvature of the plots is relatively more significant for the imidazole complex. The plots of log kaqs vs. molfraction of methanol (XMeOH) for both the substrates also deviate from linearity, the deviation being less and less marked, particularly for the N-methyl imidazole complex, as the temperature is increased. Hence preferential solvation phenomenon appears to be less significant when the N-H proton of imidazole is replaced by -CH3 group. The plots of calculated values of the transfer free energy of the dissociative transition state, cis-{[(en)2Co(B)]3+}* (B = imidazole, N-methylimidazole), relative to that of the initial state, cis-[Co(en)2(B)Br]2+, for the transfer of the ions from water to the mixed solvent, against XMeOH exhibit maxima at XMeOH = 0.06, 0.27, and 0.12, 0.36 and minima at XMeOH = 0.12 and 0.19 for cis-[(en)2Co(imH)Br]2+ and its N-methylimidazole analogue respectively which are in keeping with the solvent structural changes around the initial state and transition state of these substrates as the solvent composition is varied.Plots of activation enthalpy and entropy against molfraction of the solvent mixtures exhibit maxima and minima. This type of variations of the activation parameters, ΔH≠ and ΔS≠, with XMeOH speaks of the enthalpy and entropy changes associated with the solvent-shell reorganization of the complex ions both in the initial and in the transition states which contribute appreciably to the overall activation enthalpy and entropy of the aquation reaction.
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  • 120
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    International Journal of Chemical Kinetics 21 (1989), S. 355-365 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a relative rate method, rate constants have been determined at 296 ± 2 K for the gas-phase reactions of the OH radical with toluene, the xylenes, and the trimethylbenzenes. Using the recommended literature rate constant for the reaction of OH radicals with propene of (2.66 ± 0.40) × 10-11 cm3 molecule-1 s-1, the following rate constants (in units of 10-12 cm3 molecule-1 s-1) were obtained: toluene, 5.48 ± 0.84; o-xylene, 12.2 ± 1.9; m-xylene, 23.0 ± 3.5; p-xylene, 13.0 ± 2.0; 1,2,3-trimethylbenzene, 32.7 ± 5.3; 1,2,4-trimethylbenzene, 32.5 ± 5.0; and 1,3,5-trimethylbenzene, 57.5 ± 9.2. These data are compared with the literature values.
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  • 121
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    International Journal of Chemical Kinetics 21 (1989), S. 993-1001 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethers are being increasingly used as motor fuel additives to increase the octane number and to reduce CO emissions. Since their reaction with hydroxyl radicals (OH) is a major loss process for these oxygenated species in the atmoshpere, we have conducted a relative rate study of the kinetics of the reactions of OH radicals with a series of ethers and report the results of these measurements here. Experiments were performed under simulated atmospheric conditions; atmospheric pressure (≃ 740 torr) in synthetic air at 295 K. Using rate constants of 2.53 × 10-12, and 1.35 × 10-11 cm3 molecule-1 s-1 for the reaction of OH radicals with n-butane and diethyl ether, the following rate constants were derived, in units of 10-11 cm3 molecule-1 s-1: dimethylether, (0.232 ± 0.023); di-n-propylether, (1.97 ± 0.08); di-n-butylether, (2.74 ± 0.32); di-n-pentylether, (3.09 ± 0.26); methyl-t-butylether, (0.324 ± 0.008); methyl-n-butylether, (1.29 ± 0.03); ethyl-n-butylether, (2.27 ± 0.09); and ethyl-t-butylether, (0.883 ± 0.026). Quoted errors represent 2σ from the least squares analysis and do not include any systematic errors associated with uncertainties in the reference rate constants used to place our relative measurements on an absolute basis. The implications of these results for the atmospheric chemistry of ethers are discussed.
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  • 122
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 123
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    International Journal of Chemical Kinetics 21 (1989), S. 423-430 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of oxidation of a number of ortho, meta, and para substituted S-phenylmercaptoacetic acids by N-Chloro-3-Metyl-2,6-Diphenylpiperidin-4-one (NCP) has been studied in buffered ethanol-water (75:25 v/v) of pH 5.46. The reaction is of first order each in [oxidant] and [substrate]. The rate constant decreases with increase in pH from 5.22 to 5.70. The reaction is accelerated by electron releasing and retarded by electron withdrawing substitutents. The ρ value obtained for this reaction is -1.88 at 10°C with a good correlation coefficient of 0.99 showing an electron deficient transition state. The effect of ortho substitutents also is discussed in detail.
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  • 124
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    International Journal of Chemical Kinetics 21 (1989) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 125
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    International Journal of Chemical Kinetics 21 (1989), S. 499-517 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants of Br atom reactions have been determined using a relative kinetic method in a 20 l reaction chamber at total pressures between 25 and 760 torr in N2 + O2 diluent over the temperature range 293-355 K. The measured rate constants for the reactions with alkynes and alkenes showed dependence upon temperature, total pressure, and the concentration of O2 present in the reaction system.Values of (6.8 ± 1.4) × 10-15, (3.6 ± 0.7) × 10-14, (1.5 ± 0.3) × 10-12, (1.6 ± 0.3) × 10-13, (2.7 ± 0.5) × 10-12, (3.4 ± 0.7) × 10-12, and (7.5 ± 1.5) × 10-12 (units: cm3 s-1) have been obtained as rate constants for the reactions of Br with 2,2,4-trimethylpentane, acetylene, propyne, ethene, propene, 1-butene, and trans-2-butene, respectively, in 760 torr of synthetic air at 298 K with respect to acetaldehyde as reference, k = 3.6 × 10-12 cm3 s-1.Formyl bromide and glyoxal were observed as primary products in the reaction of Br with acetylene in air which further react to form CO, HBr, HOBr, and H2O2. Bromoacetaldehyde was observed as an primary product in the reaction of Br with ethene. Other observed products included CO, CO2, HBr, HOBr, BrCHO, bromoethanol, and probably bromoacetic acid.
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  • 126
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    International Journal of Chemical Kinetics 21 (1989), S. 561-574 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A chemical kinetic model was constructed for the pyrolysis of butylbenzene. The mechanism was based on free radical reactions. All relevant reactions were considered, and a final selection of 60 reactions involving 29 molecules and free radicals was made. The rate constants and thermodynamic parameters were taken from the literature or estimated using accepted literature methods such as group additivity. The results from the model were compared to experimental rates and product selectivity for butylbenzene pyrolysis over a temperature range of 778 K to 868 K and to an experimental rate at 923 K. The rates agreed within a factor of two and were usually much closer. The experimental and theoretical yields of the major products, styrene, ethane, toluene, and propylene, agreed within two percentage points. The agreement for seven minor products was not quite as good, with the worst case being an overprediction of the yield of allylbenzene by a factor of 2.6.
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  • 127
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    International Journal of Chemical Kinetics 21 (1989), S. 611-619 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants have been determined for the reactions of SO4- with a series of alkanes and ethers. The SO4- radical was produced by the laser-flash photolysis of persulfate, S2O82-. For methane, only an upper limit of 1 × 106 M-1 s-1 could be determined. For ethane, propane, and 2-methylpropane, rate constants of 0.44, 4.0, and 10.5 × 107 M-1 s-1 were found. For ethyl and n-propyl ether, rate constants of 1.3 × 108 and 2.2 × 108 M-1 s-1 were found and for 1,4-dioxane and tetrahydrofuran, rate constants of 7.2 × 107 and 2.8 × 108 were obtained. The reaction of SO4- with allyl alcohol was also studied and found to have a rate constant of 1.4 × 109 M-1 s-1.
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  • 128
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    International Journal of Chemical Kinetics 21 (1989), S. 667-676 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate constants for the reaction of NO3· with sulfur compounds in acetonitrile have been determined by the flash photolysis method. The rate constant for dimethyl sulfone (2.7 × 104 M-1s-1 at -10°C) is larger than that of the deuterium derivative, indicating that NO3· abstracts the hydrogen atom from dimethyl sulfone. In the case of dimethyl sulfide, the rate constant was evaluated to be 1.5 × 109 M-1 s-1 at -10°C; the transient absorption band attributable to the cation radical was observed after the decay of NO3·, suggesting the electron transfer reaction from the sulfide to NO3·. For diphenyl sulfide and dimethyl disulfide, the electron transfer reactions were also confirmed. For dimethyl sulfoxide, the reaction rate constant of 1.2 × 109 M-1 s-1 (at -10°C) was not practically affected by the deuterium substitution, suggesting that NO3· adds to sulfur atom forming (CH3)2Ṡ(O)-ONO2. On the other hand, for diphenyl sulfoxide, the electron transfer reaction occurs. By the comparison of these rate constants in acetonitrile solution with the reported rate constants in the gas phase, the change of the reaction paths was revealed.
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  • 129
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    International Journal of Chemical Kinetics 21 (1989), S. 703-714 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical reactions involving two or more intermediates and many mutual reaction channels may lead to the specific formation of one cross-reaction product if one species is rather persistent and if transient and persistent species are produced with equal rates. A previous kinetic analysis of the phenomenon revealed that the concentrations of the intermediates and the selectivities of product formation depend critically on the relative initiation rates. The present experimental ESR studies on systems involving simultaneously generated phenoxyl radicals as persistent and alkyl radicals as transient species confirm the predicted behavior. They also lead to absolute rate constants for reactions of alkyl with phenoxyl radicals and for hydrogen atom transfer from phenols to alkyl radicals.
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  • 130
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intermediate product of the reaction of MoOS2(S2CNR2)2 and PPh3 in dichloroethane has been detected by ESR spectroscopy. Two ESR signals have been observed at low temperature in the reaction system which was stopped by quenching it in liquid nitrogen. The g values are 2.020 ± 0.001 and 1.972 ± 0.001 respectively. The signal at g = 2.020 is attributed to a reaction intermediate with pentavalent molybdenum. A reaction mechanism has been proposed which is consistent with the observation of pentavalent molybdenum as the intermediate in the process of reaction.
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  • 131
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    International Journal of Chemical Kinetics 21 (1989), S. 801-827 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aromatic ring-retaining products formed from the gas-phase reactions of the OH radical with benzene and toluene, in the presence of NOx, have been identified and their formation yields determined. These products, and their formation yields, are as follows: from benzene - phenol, 0.236 ± 0.044; nitrobenzene, {(0.0336 ± 0.0078) + (3.07 ± 0.92) × 10-16[NO2]}; from toluene - benzaldehyde, 0.0645 ± 0.0080; benzyl nitrate, 0.0084 ± 0.0017; o-cresol, 0.204 ± 0.027; m- + p-cresol, 0.048 ± 0.009; m-nitrotoluene, {(0.0135 ± 0.0029) + (1.90 ± 0.25) × 10-16[NO2]}, where the NO2 concentration is in molecule cm-3 units. The formation yields of o- and p-nitrotoluene from toluene were ca. 0.07 and 0.35 that of m-nitrotoluene, respectively. The observations that the nitro-aromatic yields do not extrapolate to zero as the NO2 concentration approaches zero are not consistent with current chemical mechanisms for these OH radical-initiated reactions, and suggest that under the experimental conditions employed in this study the hydroxycyclohexadienyl radicals formed from OH radical addition to the aromatic ring react with NO2 rather than with O2. However, these data concerning the nitroaromatic yields are consistent with our previous conclusions that many of the nitrated polycyclic aromatic hydrocarbons present in ambient air are formed, at least in part, in the atmosphere from OH radical reactions.
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  • 132
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    Topics: Chemistry and Pharmacology
    Notes: A modified laser photolysis/laser-induced fluorescence technique has been used to measure atmospheric pressure absolute rate coefficients for the reaction of hydroxyl (OH) radicals with the chlorinated methanes (CH3Cl, CH2Cl2, and CHCl3). Data have been obtained for these compounds over the widest temperature range (292-800 K) that has been reported in the literature using a single experimental apparatus. The temperature dependence of the rate data is best represented by the following three-parameter expressions: \documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}_{\rm 3} {\rm Cl:}\,{\rm 8}{\rm .38}\,\, \pm \,\,1.07\,\, \times \,\,10^{ - 16} \,{\rm T}^{{\rm 1}{\rm .38} \pm {\rm 2}{\rm .01/0}{\rm .71}} \exp [- 2387.4\,\, \pm \,\,142.8/RT]({\rm cm}^3 /{\rm molec - s)}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}_{\rm 2} {\rm Cl}_{\rm 2} {\rm :}\,\,1.{\rm 52}\,\, \pm \,\,0.16\,\, \times \,\,10^{ - 16} \,{\rm T}^{{\rm 1}{\rm .58} \pm 0.45} \exp [- 1236.3\,\, \pm \,\,119.5/RT]({\rm cm}^3 /{\rm molec - s)}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm CHCl}_{\rm 3} {\rm :}\,\,1.{\rm 92}\,\, \pm \,\,0.21\,\, \times \,\,10^{ - 20} \,{\rm T}^{{\rm 2}{\rm .78} \pm 0.34/0.42} \exp [- 188.3\,\, \pm \,\,119.3/RT]({\rm cm}^3 /{\rm molec-s)}$$\end{document} Uncertainties in the pre-exponential and exponential term are expressed as 95% confidence intervals. For the temperature exponent, error limits represent a ±10% change in the total error of best fit.The degree of curvature in the Arrhenius plots appeared to increase with increasing Cl substitution of the reactant. However, the uncertainty in the temperature exponent for the CH3Cl data was large in comparison with the other chlorinated methanes. Thus, data of greater precision at elevated temperatures are necessary to further explore this relationship. The rate coefficients were compared with recent semiempirical and transition state theory models for haloalkane-OH hydrogen transfer reactions over a temperature range of 250-800 K. The transition state model of Cohen and Benson was in excellent agreement with the CH3Cl and CH2Cl2 data. The semiempirical structure activity relationship developed by Atkinson represented the best fit of the CHCl3 data, although it underestimated the experimental data by more than a factor of 2 at 800 K. The extreme care used to remove and alayze for reactive impurities along with the agreement with other experimental studies suggests that transition state and semi-empirical models for CHCl3 must be modified to account its reaction behavior at high temperature.
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  • 133
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    International Journal of Chemical Kinetics 21 (1989), S. 233-243 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that kinetic data on the polymerization of acetylene to vinyl acetylene and benzene can be reconciled with the formation of a 1,4 biradical which can isomerize by a 1-3, H-atom shift to the molecular product. Since the biradicals have a negligibly small life-time in the system the overall process appears to be a concerted bimolecular reaction. The labile isomer CH2 = C: which had been suggested as being the reactive intermediate, is argued on energy considerations not to be a plausible intermediate.Data on the reverse pyrolysis of vinyl acetylene to acetylene are consistent with the model. Extending the model to butadiene explains the observed molecular nature of its decomposition to ethylene and acetylene.Reactions of other oligomers of acetylene are discussed.
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  • 134
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of the kinetics of thermal unimolecular decomposition of methylcyclopentane, methylcyclohexane, ethynylcyclopentane, and ethynylcyclohexane have been carried out at temperatures in the range 861-1218 K using the technique of very low-pressure pyrolysis (VLPP). Multiple reaction pathways and secondary decomposition of primary products results in a complex array of reaction products. VLPP rate data (fall-off regime) were obtained for the overall decompositions and interpreted via the application of RRKM theory. The data for methylcyclopentane and methylcyclohexane were interpreted in terms of ring-opening bond fission pathways and bond fission to methyl and cycloalkyl radicals. By selecting Arrhenius parameters consistent with the analogous pathways in open-chain alkanes, a good fit to the overall decomposition is obtained. The data for ethynylcyclopentane and ethynylcyclohexane were interpreted in terms of ring-opening bond fission and alkyne to allene isomerization. The A factors for ring opening were based on known values for C-C fission in open-chain alkynes and the Arrhenius parameters for isomerization were chosen to be consistent with previously reported alkyne to allene isomerizations. The VLPP data are consistent with the following high-pressure rate expressions (at 〈 T 〉 = 1100 K) for the dominant primary reaction channel of ring opening adjacent to the substitutent group: \documentclass{article}\pagestyle{empty}\begin{document}$$\log (k/s^{ - 1} ) = (16.4 \pm 0.3) - (341 \pm 10)/\theta {\rm for methylcyclopentane,}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\log (k/s^{ - 1} ) = (16.4 \pm 0.3) - (345 \pm 10)/\theta {\rm for methylcyclopentane,}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\log (k/s^{ - 1} ) = (16.0 \pm 0.3) - (304 \pm 10)/\theta {\rm for ethynylcyclpentane, and}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$\log (k/s^{ - 1} ) = (16.0 \pm 0.3) - (303 \pm 10)/\theta {\rm for ethynylcyclohexane,}$$\end{document} where θ = 2.303RT kJ mol-. Comparison of the activation energies for the ethynyl-cycloalkanes with those for the methyl-cycloalkanes shows that the effect of the ethynyl substituent is consistent with the propargyl resonance energy. This evidence supports the assumption of a biradical mechanism for ring opening in these cycloalkanes.
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  • 135
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    International Journal of Chemical Kinetics 21 (1989), S. 297-314 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from Smoluchowski's hypothesis, a simple algorithm is developed in order to obtain the apparent rate constant at large values of time, t, with some physical and chemical processes, as in the case of diffusion controlled reactions. Some practical examples are illustrated, assuming nonuniform distribution function, space-dependent diffusion coefficient or short-range interaction leading to an asymptotic analytical expression of the form α + β/√t, where α and β are constants function of the system of interest.
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  • 136
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    International Journal of Chemical Kinetics 21 (1989), S. 399-421 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of oxidation of 2,2′-azinobis-(3-ethylbenzothiazole-6-sulphonate) (ABTS) by the inorganic peroxides, peroxomonosulphate, peroxodisulphate, peroxodiphosphate, and hydrogen peroxide were investigated in aqueous solution. The kinetics of formation of the radical cation, ABTS.+, on one-electron abstraction by these peroxides and the further reaction of ABTS.+ with higher concentrations of these peroxides at longer time scale were studied by following the growth and decay of the radical cation, ABTS.+ at 417 nm. The rate of formation of ABTS.+ was found to obey a total second-order, first-order each in [ABTS] and [peroxide], except for H2O2, which reacted through Michaelis-Menten kinetics. All the peroxides investigated were found to react with ABTS.+; however peroxodisulphate alone oxidized ABTS.+ to the dication (ABTS++), the other peroxides reacted via ionic mechanism, probably forming sulphoxide and sulphone as products. The kinetics of decay of the radical cation, ABTS.+, was also found to follow a total second-order, first-order each in [ABTS.+] and [peroxide], except peroxodiphosphate the reaction of which obeyed Michaelis-Menten kinetics. The effect of pH and temperature were also investigated in all the systems and the kinetic and thermodynamic parameters were evaluated and discussed with suitable reaction mechanisms.
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  • 137
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    International Journal of Chemical Kinetics 21 (1989), S. 445-464 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An earlier correlation between isolated CH stretching frequencies, visCH, and experimental CH bond dissociation energies, in hydrocarbons, fluorocarbons, and CHO compounds, is updated. A stabilization energy, EvS, which reflects only the properties of the radical, is defined by the deviation of a point from the above correlation. EvS values for a variety of radicals are listed and discussed. In H—C—N and H—C—O compounds EvS is low or negligible, due to the low visCH found in these compounds. The conventional definition of ES then represents a serious misnomer, which distracts attention from the probable source of discrepancies between experimental and ab initio values of DH°(C—H), namely, the parent molecules. Stereo electronic effects concerned with the breaking of CH bonds are predicted in a variety of situations.Some experimental determinations of DH°(C—H), viz., in C2H4, HCOOH, CH3CHO, CH3NH2, are considered to be probably in error.Schemes for partitioning energies of atomization into ‘standard’ or ‘intrinsic’ bond energies are criticized.
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  • 138
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    International Journal of Chemical Kinetics 21 (1989), S. 547-560 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenol pyrolysis has been studied in a turbulent flow reactor by analyzing concentration-time profiles of three major decomposition products: carbon monoxide, cyclopentadiene, and benzene. Experimental conditions were P = 1 atm, T = 1064 - 1162 K, and initial phenol concentrations of 500-2016 ppm. The major experimental observations were that the decomposition product profiles were nearly linear as a function of time and that the overall rate of carbon monoxide production was greater than that of cyclopentadiene. The rate difference is explained by a mechanism which includes a radical combination reaction of cyclopentadienyl and phenoxy. With literature and approximate rate coefficient data, the mechanism reproduced the experimental observations very well. The mechanism and data provide estimates of rate coefficients for the phenol decomposition initiation step, abstraction of hydrogen from phenol by cyclopentadienyl, and the phenoxy-cyclopentadienyl combination, all of which have not been available in the literature.
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  • 139
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    International Journal of Chemical Kinetics 21 (1989) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 140
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    International Journal of Chemical Kinetics 21 (1989), S. 677-687 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants have been determined for the reactions of SO4- with a series of alcohols, including hydrated formaldehyde. The SO4- radical was produced by the laser-flash photolysis of persulfate, S2O82-. Rate constants for the reactions of SO4- with alcohols range from 1.0 × 107 for methanol to 3.4 × 108 M-1 s-1 for 1-octanol. Rate constants for the reactions of SO4- with deuterated methanol and ethanol are lower by about a factor of 2.5. For methanol, ethanol, and 2-propanol, the temperature dependence of the rate constant was determined over the range 10-45°C.
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  • 141
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    International Journal of Chemical Kinetics 21 (1989) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 142
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    International Journal of Chemical Kinetics 21 (1989), S. 967-976 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selectivity-reactivity correlations are shown to support a biradical pathway for the gas phase thermal Diels-Alder reactions of cyclohexa-1,3-diene with substituted ethenes except for those involving a carbonyl group.
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  • 143
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate coefficients were calculated for vibrational relaxation and collision-induced dissociation of ground state xenon fluoride in neon at temperatures between 300 and 1000 K for each of nine vibrational levels. These coefficients were calculated using a pairwise additive potential energy surface, which consists of a Morse function for the XeF interaction and Lennard-Jones functions for the NeXe and NeF interactions. Rate coefficients are provided for both temperature and v- dependences. The vibrational relaxation and dissociation processes occur by multiquanta transitions. Dissociation can take place from all v-levels provided that the internal energy of the XeF molecule is close to the rotationless dissociation limit. The order of increase effectiveness of the various forms of energy in promoting dissociation in XeF was found to be translation-rotation-vibration. At room temperature, neon atoms were found to be more efficient than helium atoms in the dissociation processes; helium atoms were found to be more efficient than neon atoms in the vibrational relaxation of XeF. Strong vibration-rotation coupling in both vibrational relaxation and in the dissociation processes is demonstrated.
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  • 144
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    International Journal of Chemical Kinetics 21 (1989), S. 1049-1067 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high temperature kinetics of NH in the pyrolysis of isocyanic acid (HNCO) have been studied in reflected shock wave experiments. Time histories of the NH(X3Σ-) radical were measured using a cw, narrow-linewidth laser absorption diagnostic at 336 nm. The second-order rate coefficients of the reactions: were determined to be: \documentclass{article}\pagestyle{empty}\begin{document}$$k_{1{\rm a}} = 9.84\,\, \times \,\,10^{15} \,\,\exp (- 43000/T,{\rm K})\,\,\,\,\,\,(f = 0.65,F = 1.50)\,\,\,\,\,\,T = 1830 - 3340\,\,{\rm K,}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm 2} = 5.1\,\, \times \,\,10^{13} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(f = 0.7,F = 1.3)\,\,\,\,\,\,T = 2070 - 2730\,\,{\rm K,}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm 3} = 2.65\,\, \times \,\,10^{14} \,\,\,\exp (- 38000/T,{\rm K})\,\,\,\,\,\,(f = 0.5,F = 1.4)\,\,\,\,\,\,T = 3140 - 3320\,\,{\rm K,}$$\end{document} cm3-mol-1-s-1, where f and F define the lower and upper uncertainty limits, respectively. The data for k1a are somewhat better fit by: \documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm 1a}} = 3.26\,\, \times \,\,10^{35} T^{ - 5.11} \,\,\exp (- 55300/T,{\rm K})\,\,\,{\rm cm}^{\rm 3} {\rm - mol}^{{\rm - 1}} {\rm - s}^{{\rm - 1}} .$$\end{document}
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  • 145
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    International Journal of Chemical Kinetics 21 (1989), S. 1095-1100 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics and products of the decomposition of 9-diazofluorene by tris (p-bromophenyl) aminium hexachloroantimonate in acetonitrile solvent has been investigated. The reaction is first order with respect to the concentration of both 9-diazofluorene and tris (p-bromophenyl) aminium hexachloroantimonate. A reaction mechanism has also been proposed.
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  • 146
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    International Journal of Chemical Kinetics 21 (1989), S. 1131-1139 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pressure-jump method has been used to determine the rate constants for the formation and dissociation of nickel(II) and cobalt(II) complexes with cinchomeronate in aqueous solution at zero ionic strength. The forward and reverse rate constants obtained are kf = 2.27 × 106 M-1 s-1 and kr = 3.81 × 101 s-1 for the nickel(II) complex and kf = 1.23 × 107 M-1 s-1 and kr = 2.66 × 102 s-1 for the cobalt(II) complex at 25°C. The activation parameters of the reactions have also been obtained from the temperature variation study. The results indicate that the rate determining step of the reaction is a loss of a water molecule from the inner coordination sphere of the cation for the nickel(II) complex and the chelate ring closure for the cobalt(II) complex. The influence of the pyridine ring nitrogen atom of the cinchomeronate ligand on the complexation of cobalt(II) ion is also discussed.
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  • 147
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    International Journal of Chemical Kinetics 21 (1989), S. 315-330 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of oxidation of aliphatic amines viz., ethylamine, n-butylamine, isopropylamine (primary amines), diethylamine (secondary amine), and triethylamine (tertiary amine) by chloramine-T have been studied in NaOH medium catalyzed by osmium (VIII) and in perchloric acid medium with ruthenium(III) as catalyst. The order of reaction in [Chloramine-T] is always found to be unity. A zero order dependence of rate with respect to each [OH-] and [Amine] has been observed during the osmium(VIII) catalyzed oxidation of diethylamine and triethylamine while a retarding effect of [OH-] or [Amine] on the rate of oxidation is observed in case of osmium(VIII) catalyzed oxidation of primary aliphatic amines. The ruthenium(III) catalyzed oxidation of amines follow almost similar kinetics. The order of reactions in [Amine] or [Acid] decreases from unity at higher amine or acid concentrations.The rate of oxidation is proportional to {k′ and k″ [Ruthenium(III)] or [Osmium(VIII)]} where k′ and k″ (having different values in case of ruthenium(III) and osmium(VIII)) are the rate constants for uncatalyzed and catalyzed path respectively. The suitable mechanism consisting with the kinetic data is proposed in each case and discussed.
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  • 148
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    International Journal of Chemical Kinetics 21 (1989), S. 1069-1076 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relative rate technique has been used to determine rate constants for the reaction of bromine atoms with a variety of organic compounds. Decay rates of the organic species were measured relative to i-butane or acetaldehyde or both. Using rate constants of 1.74 × 10-15 and 3.5 × 10-12 cm3 molecule-1 s-1 for the reaction of Br with i-butane and acetaldehyde respectively, the following rate constants were derived, in units of cm3 molecule-1 s-1: 2, 3-dimethylbutane, (6.40 ± 0.77) × 10-15; cyclopentane, (1.16 ± 0.18) × 10-15, ethene, (≤2.3 × 10-13); propene, (3.85 ± 0.41) × 10-12; trans-2-butene, (9.50 ± 0.76) × 10-12, acetylene, (5.15 ± 0.19) × 10-15; and propionaldehyde, (9.73 ± 0.91) × 10-12. Quoted errors represent 2σ and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295 ± 2 K and atmospheric pressure of synthetic air or nitrogen. The results are discussed with respect to the mechanisms of these reactions and their utility in serving as a laboratory source of alkyl and alkyl peroxy radicals.
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  • 149
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    International Journal of Chemical Kinetics 21 (1989), S. 1123-1129 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a relative rate method, rate constants for the gas-phase reactions of the OH radical with 1- and 2-propyl nitrate, 1- and 2-butyl nitrate and 1-nitrobutane have been determined in the presence of one atmosphere of air at 298 ± 2 K. Using rate constants for the reactions of the OH radical with propane and cyclohexane of 1.15 × 10-12 and 7.49 × 10-12 cm3 molecule-1 s-1, respectively, following rate constants (in units of 10-12 cm3 molecule-1 s-1) were obtained: 1-propyl nitrate, 0.62; 2-propyl nitrate, 0.41; 1-butyl nitrate, 1.78; 2-butyl nitrate, 0.93; and 1-nitrobutane, 1.35. These rate constants are compared and discussed with the literature data.
    Additional Material: 3 Ill.
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  • 150
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    International Journal of Chemical Kinetics 21 (1989), S. 1153-1160 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Uncertainty sometimes exists in determining initial reaction rates from experimental data. A method, originally proposed by Wilkinson [9] for estimating orders and rate constants for simple batch nth order reactions, has been generalized to complex kinetic systems. This method yields very accurate initial rates for all systems and extends the conversion range of experimental investigation of initial rates well beyond the “zero-order” region. Accurate initial rates are required in analytical methods used for screening alternate reaction mechanisms.
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  • 151
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    International Journal of Chemical Kinetics 21 (1989), S. 1173-1180 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the flash photolysis resonance fluorescence technique, absolute rate constants were determined for the gas phase reactions of hydroxyl radicals with a series of aliphatic polyethers. At 298 K, the measured rate constants (in units of 10-12 cm3 molecule-1 s-1) were: 2,2-dimethoxypropane, (3.9 ± 0.2); 2,2-diethoxypropane, (11.7 ± 1.3); 1,2-dimethoxypropane, (14.3± 1.5); 2-methoxyethylether, (17.5 ± 1.1); 2-ethoxyethlyether, (26.8 ± 2.4); 1,1-dimethoxyethane, (8.9 ± 1.0); and 1,1,3-trimethoxypropane, (16.7 ± 1.0).The temperature dependencies of the rate constants for 2,2-dimethoxypropane and 2,2-diethoxypropane, reactions (1) and (2), were studied over the temperature range 240-440 K and are expressed by the Arrhenius equations: \documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm 1} = (3.55\,\, \pm 0.39)\,\, \times \,\,10^{ - 12} \,\,\exp [(30 \pm 35)\,/T]\,\,{\rm cm}^{\rm 3} \,\,{\rm molecule}^{{\rm - 1}} {\rm s}^{{\rm - 1}}$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm 2} = (1.06\,\, \pm 0.25)\,\, \times \,\,10^{ - 11} \,\,\exp [(15 \pm 75)\,/T]\,\,{\rm cm}^{\rm 3} \,\,{\rm molecule}^{{\rm - 1}} {\rm s}^{{\rm - 1}}$$\end{document} Implications of the results are discussed in terms of reaction mechanisms and the prediction of gas phase OH radical reaction rates for aliphatic polyethers.
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  • 152
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    International Journal of Chemical Kinetics 21 (1989), S. 115-150 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 153
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    International Journal of Chemical Kinetics 21 (1989), S. 157-163 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The heat of formation of benzophenone oxide, Ph2CO2, was measured using photoacoustic calorimetry. The enthalpy of the reaction Ph2CN2 + O2 → Ph2CO2 + N2 was found to be -48.0 ±0.8 kcal mol-1 and ΔHf(Ph2CN2) was determined by measuring the reaction enthalpy for Ph2CN2 + EtOH → Ph2CHOEt + N2 (-53.6 ±1.0 kcal mol-1). Taking ΔHf(PhCHOEt) = -10.6 kcal mol-1 led to ΔHf(Ph2CN2) = 99.2 ± 1.5 kcal mol-1 and hence to ΔHf(Ph2CO2) = 51.1 ± 2.0 kcal mol-1. The results imply that the self-reaction of benzophenone oxide i.e., 2Ph2CO2 → 2Ph2CO + O2 is exothermic by -76.0 ±4.0 kcal mol-1.
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  • 154
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    International Journal of Chemical Kinetics 21 (1989), S. 175-191 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Methylbut-1-ene-3-yne and Propyne mixtures were pyrolyzed at 350-450°C in the absence and presence of O2 and NO. The major product of the reaction is a polymer, but m-xylene and p-xylene are also produced and were studied as the species of interest. The C8H10 formation rate is first-order in C3H4 and C5H6. The rate coefficient is best fitted by \documentclass{article}\pagestyle{empty}\begin{document}$$\log [k({\rm C}_{\rm 8} {\rm H}_{{\rm 10}}),M^{ - 1} s^{ - 1}] = (11.2 \pm 1.0) - (166 \pm 13)/2.3RT$$\end{document} though it is not inconsistent with \documentclass{article}\pagestyle{empty}\begin{document}$$\log [k({\rm C}_{\rm 8} {\rm H}_{{\rm 10}}),M^{ - 1} s^{ - 1}] = (8.17) - (125.9)/2.3RT$$\end{document} where R is the ideal gas constant in kJ/mol-K. Experiments in the presence of NO show that m-xylene and p-xylene formation occur by two processes: a concerted molecular mechanism (≃ 41%) and a singlet diradical mechanism (≃ 59%).
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  • 155
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    International Journal of Chemical Kinetics 21 (1989), S. 227-232 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Flash Vaccum Pyrolysis of (α-phenylethyl) and (β-phenylethyl)-pyrazole were studied. Pyrazole and Styrene were found as only products of both reactions. The kinetic parameters obtained reinforce the results previously found about the poor influence of the substitutents on the α and β carbons of the ethyl group in the FVP of N-alkyl pyrazoles and (β-haloethyl) pyrazoles.
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  • 156
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-chloro-3-aminopropanol was obtained in aqueous solution by mixing the amine with the hypochlorite. The first order decomposition kinetics of the N-chloramine in strongly alkaline media are explained by a mechanism in which the rate controlling step is the formation of an imine which is subsequently hydrolyzed. Spectrophotometry of the reaction in acid media showed that under these conditions dichloramines are formed: the second order experimental kinetics of this process are explained by a mechanism in which the rate-controlling step is a reaction between the protonated and free forms of the N-chloramine.
    Additional Material: 5 Ill.
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  • 157
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    International Journal of Chemical Kinetics 21 (1989), S. 367-371 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The elimination kinetics of 2-chloropropionic acid have been studied over the temperature range of 320-370.2°C and pressure range of 79-218.5 torr. The reaction in seasoned vessel and in the presence of the free radical suppressor cyclohexene, is homogeneous, unimolecular, and obeys a first-order rate law. The dehydrochlorination products are acetaldehyde and carbon monoxide. The rate coefficient is expressed by the following Arrhenius equation: log k1(s-1) = (12.53 ± 0.43) - (186.9 ± 5.1) kJ mol-1 (2.303RT)-1. The hydrogen atom of the carboxylic COOH appears to assist readily the leaving chloride ion in the transition state, suggesting an intimate ion pair mechanism operating in this reaction.
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  • 158
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    International Journal of Chemical Kinetics 21 (1989), S. 635-642 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Relaxation rate constants for the collisional deactivation of I (2P1/2) by halogen cyanides were measured by time resolved atomic absorption. The values obtained were (1.2 ± 0.1) × 10-15, (5.2 ± 0.7) × 10-15, and (2.6 ± 0.4) × 10-14 cm3 molecule-1 s-1 for ClCN, BrCN, and ICN, respectively. Quenching efficiencies are discussed in view of the stability of linear molecules to form the transient complex as well as the similarities assumed between halogen cyanides and interhalogen diatomic molecules.
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  • 159
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    International Journal of Chemical Kinetics 21 (1989), S. 757-763 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The catalytic activity of iodine monobromide and iodine monochloride were investigated in the reaction, Et3SiOBun + BusOH ⇌ Et3SiOBus + BunOH. Pseudo first-order rate constants were measured by gas chromatography, at 10°, 20°, 30°, and 40°C for iodine monobromide and at 10°, 20°, and 30°C for iodine monochloride, on reaction mixtures containing both butanols in excess. The catalytic coefficients of both catalysts were evaluated from the observed rate constants as follows: \documentclass{article}\pagestyle{empty}\begin{document}$$k_{2{\rm IBr}} = 9.5 \pm 10^8 \exp \,(- 54.8 \times 10^3 /RT)$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$k_{ - 2{\rm IBr}} = 12.3 \pm 10^8 \exp \,(- 53.3 \times 10^3 /RT)$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$k_{2{\rm ICI}} = 10.7 \pm 10^8 \exp \,(- 54.6 \times 10^3 /RT)$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$k_{ - 2{\rm ICI}} = 13.2 \pm 10^8 \exp \,(- 53.1 \times 10^3 /RT)$$\end{document}The activation paramaters were estimated from these data, and were compared with the values for iodine catalysis. These results are consistent with the mechanism previously proposed.
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  • 160
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    International Journal of Chemical Kinetics 21 (1989), S. 765-774 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pulsed laser photolysis/laser-induced fluorescence (LIF) is utilized to measure absolute rate constants of CH radical reactions as a function of temperature and pressure. Multiphoton dissociation of CHBr3 at 266 nm is employed for the generation of CH (X2Π) radicals. The CH radical relative concentration is monitored by exciting fluorescence on the R1(2) line of the (A2Δ - X2Π) transition at 429.8 nm. A resistively heated cell allows temperature studies to be performed from room temperature to ≈670 K. The following Arrhenius equations are derived: \documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm N}_{\rm 2} {\rm O,}\,\,\,\,\,\,\,\,k = (1.59 \pm 0.20)\, \times \,\,10^{ - 11} \,\,\exp [(500 \pm 45)/T]{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}};$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm SO}_{\rm 2} {\rm ,}\,\,\,\,\,\,\,\,k = (1.32 \pm 0.17)\, \times \,\,\,10^{ - 10} \,\,\exp [(250 \pm 45)/T]\,\,{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}};$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm OCS,}\,\,\,\,\,\,\,\,k = (1.99 \pm 0.11)\, \times \,\,\,10^{ - 10} \,\,\exp [(190 \pm 20)/T]\,\,{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}};$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm CS}_{\rm 2} {\rm ,}\,\,\,\,\,\,\,\,k = (3.49 \pm 0.36)\, \times \,\,\,10^{ - 10} \,\,\exp [- (40 \pm 35)/T]\,\,{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}};$$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$${\rm CH}\,{\rm + }\,{\rm SF}_{\rm 6} {\rm ,}\,\,\,\,\,\,\,\,k 〈 5\,\,\, \times \,\,\,10^{ - 17} {\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}} .$$\end{document} With the exception of SF6, the reactions of sulfur containing species proceed at rates that are near the theoretical gas kinetic collision frequency. Additionally, these reactions all have activation energies that are near zero or slightly negative. These observations are consistent with an insertion-decomposition mechanism being dominant under these conditions.
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  • 161
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    International Journal of Chemical Kinetics 21 (1989), S. 847-858 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Second order rate constants for C2H2 or C2D2 polymerizations into vinylacetylene and higher CnHn products have been measured in a static reactor by dynamic mass spectrometry between 770-980 K. They are nearly identical within experimental error (±50%). It is shown that these results are consistent with the participation of thermally equilibrated vinylidene H2C = C: as a reactive intermediate: since this assumption only introduces a modest reverse equilibrium isotope effect (KiH/KiD ca. 0.48 in this range) into overall rate constants. At the same time they seem to discriminate in general against alternative mechanisms in which the required H-atom transfers take place in rate determining steps. Present evidence, in conjunction with an updated analysis of relevant issues such as experimental and theoretical vs. termochemical estimates of the heat of formation of H2C=C:, the nature of the transition states of singlet vinylidene addition reactions and the likelihood of discrete biradical intermediates in C2H2 dimerization, seems to lend further support to the notion that acetylene behaves as a singlet carbene at high temperatures.
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  • 162
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements from previous studies have shown that when hydroxyl radicals react with various chlorinated hydrocarbons under atmospheric conditions, free chlorine atoms can be produced. In one such study (Edney et al., [3]) from an analysis of the rate equations under a strict set of assumptions, Cl-atom yields could be inferred. Since the approach was indirect, a more direct method for obtaining these yields has been developed. The technique described in this study involves scavenging Cl atoms produced by the reaction (using ethylene or propylene as the scavenger) and then measuring the yield of the stable chlorinated product generated. Cl-atom yields were determined for allyl chloride, vinyl chloride, vinylidene chloride, trichloroethylene, and benzyl chloride. The experiments were performed by irradiating mixtures of CH3ONO/NO/chlorinated hydrocarbon/alkene in air in 150-L Teflon chambers. The yields for the reaction of Cl atoms with the alkenes generating the stable products were determined in seperate experiments. Yields for the formation of Cl atoms upon reaction with hydroxyl radicals are as follows (with 1 σ deviation): allyl chloride: 0.37 ± 0.10, vinyl chloride: 0.04 ± 0.01, vinylidene chloride: 0.23 ± 0.09, trichloroethylene: 0.63 ± 0.34, and benzyl chloride: 0.08 ± 0.03.
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  • 163
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    International Journal of Chemical Kinetics 21 (1989), S. 959-966 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transient diaryl disulfide radical anions (RSSR-) were produced in nonaqueous solutions at room temperature by the flash photolysis of a solution of arylthiolate ion pair in the presence of the excess corresponding disulfide. The transient spectra were almost identical with those obtained from γ-radiolysis of the disulfides in 77 K 2-methyl-tetrahydrofuran (MTHF) glassy matrix. The spectra of disulfide radical anions in nonaqueous solutions were changed by cations, solvents, and para-substituents depending on the ion pair properties. The tighter ion pairs showed a shift of absorption band to the shorter wavelength. The disulfide radical anions decay by a unimolecular dissociation reaction to yield thiolate anion and thiyl radical. The decay kinetics were first-order in the initial time region. The rate constants obtained were changed by the counter cations in the order Na+ 〉 K+ 〉 Cs+ 〉 Li+, and by solvents. The tighter ion pairs of the disulfide radical anions showed faster dissociation reaction. This is due to stabilization of a transition state with the counter cation.
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  • 164
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    International Journal of Chemical Kinetics 21 (1989), S. 1015-1027 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal reaction of CH2O with NO2 has been investigated in the temperature range of 393-476 K by means of FTIR product analysis. Kinetic modeling of the measured CH2O, NO, CO, and CO2 concentration time profiles under varying reaction conditions gave rise to the rate constants for the following key reactions: and The error limits shown represent only the scatter (±1 σ) of the modeled values. In the modeling, the total rate constant for the CHO + NO2 reaction, k2 + k3, was not varied and the value reported by Gutman and co-workers (ref. [8]) was used for the whole temperature range investigated here. The proposed reaction mechanism, employing these newly established rate constants, can quantitively account for nearly all measured product yields, including the [CO]/([CO] + [CO2]) ratios reported by earlier workers.
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  • 165
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    International Journal of Chemical Kinetics 21 (1989), S. 1077-1089 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fourier transform infrared spectroscopy was used to identify and quantify products of the self reaction of ethylperoxy radicals, C2H5O2, formed in the photolysis of Cl2/C2H6 mixtures in 700 torr total pressure of synthetic air at 295 K. From these measurements, branching ratios for the reaction channels of k1a/(k1a + k1b) = 0.68 and k1c/(k1a + k1b + k1c) ≤ 0.06 were established. Additionally, using the relative rate technique, the rate constant for the reaction of Cl atoms with C2H5OOH was determined to be (1.07 ± 0.07) × 10-10 × cm3 molecule-1 s-1. Results are discussed with respect to the previous kinetic and mechanistic studies of C2H5O2 radicals.
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  • 166
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    International Journal of Chemical Kinetics 21 (1989), S. 1101-1112 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas phase reaction of OH radicals with dimethyl sulfide (CH3SCH3, DMS) has been studied using both an absolute and a relative technique at 295 ± 2 K and a total pressure of 1 atm. The absolute rate technique of pulse radiolysis combined with kinetic spectroscopy was applied. Using this technique a rate constant of (3.5 ± 0.2) × 10-12 cm3 molecule-1 s-1 was obtained. For the relative rate method, rate constants for the reaction of OH with DMS were found to increase with increasing concentrations of added NO. These results are compared with the large body of kinetic and mechanistic data previously reported in the literature.
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  • 167
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    International Journal of Chemical Kinetics 21 (1989), S. 1141-1152 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase reaction of methyl vinyl ketone with the OH radical, in the presence of NOx, was investigated at 298 ± 2 K and atmospheric pressure of air. Glycolaldehyde and methylglyoxal were observed to be the major products, with a combined yield of 0.89 ± 0.16. The sum of the yields of the two other main products, formaldehyde and peroxyacetyl nitrate, were found to be essentially unity. The product yield data for glycolaldehyde and methylglyoxal indicate that OH radical addition to the terminal carbon atom of the 〉C=C〈 bond accounts for 72 ± 21% of the overall reaction, with the remaining 28 ± 9% proceeding via addition to the inner carbon atom of the double bond.
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  • 168
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    International Journal of Chemical Kinetics 9 (1977), S. 31-53 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The decomposition of dimethyl peroxide (DMP) was studied in the presence and absence of added NO2 to determine rate constants k1 and k2 in the temperature range of 391-432°K: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{rcl} {{\rm DMP}} & \stackrel{1}{\longrightarrow} & {2{\rm MeO}} \\ {{\rm MeO + DMP}} & \stackrel{2}{\longrightarrow} & {{\rm MeOH + CH}_{\rm 2} {\rm O} + {\rm MeO}} \\ \end{array} $$\end{document} The results reconcile the studies by Takezaki and Takeuchi, Hanst and Calvert, and Batt and McCulloch, giving log k1(sec-1) = (15.7 ± 0.5) - (37.1 ± 0.9)/2.3 RT and k2 ≈ 5 × 104M-1· sec-1. The disproportionation/recombination ratio k7b/k7a = 0.30 ± 0.05 was also determined: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{rcl} {{\rm MeO} + {\rm NO}_2 (+ {\rm M})} \stackrel{7a}{\longrightarrow} & {{\rm MeONO}_{\rm 2} (+ {\rm M})} \\ {{\rm MeO} + {\rm NO}_2} \stackrel{7b}{\longrightarrow} & {{\rm CH}_{\rm 2} {\rm O} + {\rm HONO}} \\ \end{array} $$\end{document}When O2 was added to DMP mixtures containing NO2, relative rate constants k12/k7a were obtained over the temperature range of 396-442°K: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{rcl} {{\rm CH}_{\rm 3} {\rm O} + {\rm O}_2} \stackrel{12}{\longrightarrow} & {{\rm CH}_2 {\rm O} + {\rm HO}_{\rm 2}} \\ \end{array} $$\end{document} A review of literature data produced k7a = 109.8±0.5M-1·sec-1, giving log k12(M-1·sec-1) = (8.5 ± 1.5) - (4.0 ± 2.8)/2.3 RT, where most of the uncertainty is due to the limited temperature range of the experiments.
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  • 169
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    International Journal of Chemical Kinetics 9 (1977), S. 123-131 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By means of the technique of laser-induced fluorescence, the room-temperature vibrational relaxation of DF(v = 1) has been studied in the presence of several polyatomic chaperones. The rate coefficients obtained [in units of (μ;sec·torr)-1] are CH4, 0.22; C2H6, 0.61; C4H10, 1.26; C2H2, 4.0 × 10-2; C2H2F2, 1.86 × 10-2; C2H4, 0.175; CH3F, 0.36; CF3H, 1.95 × 10-2; CF4, 1.0 × 10-3; CBrF3, 5.6 × 10-4; NF3, 5.1 × 10-4; SO2, 1.27 × 10-2; and BF3, 7.1 × 10-3. Results are also reported for vibrational relaxation rate coefficients for HF(v = 1) in the presence of the following chaperones: CH4, 2.6 × 10-2; C2H6, 5.9 × 10-2; C3H8, 8.4 × 10-2; and C4H10, 0.128. A comparison of DF and HF results indicates that for deactivation by CnHn+2, rate coefficients for DF are approximately an order of magnitude larger than for HF. The deactivation rate coefficient of DF(v = 1) by CH4 was found to decrease with increasing temperature between 300 and 740°K.
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  • 170
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    International Journal of Chemical Kinetics 9 (1977), S. 1-12 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions between alizarin yellow G and six different bases B (including OH-) and between tropaeolin 0 and eight different bases have been investigated at 25°C and an ionic strength of 0.5M, using the temperature-jump method. From the form of the log kB versus ΔpK curves it is concluded that for alizarin yellow G the observed relaxation time is due chiefly to a diffusion-controlled reaction between the base and that fraction which is present in the “open” non-hydrogen-bonded form, whereas for tropaeolin 0 the base attacks the hydrogen bridge.The dissociation constants for the internally bound hydrogen have been measured under the same conditions of temperature and ionic strength, using a spectrophotometric method.
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  • 171
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    International Journal of Chemical Kinetics 9 (1977), S. 67-81 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 1,3-cyclopentadiene (CPD) with ground-state atomic oxygen O(3P), produced by mercury photosensitized decomposition of nitrous oxide, was studied. The identified products were carbon monoxide and the following C4H6 isomers: 3-methylcyclopropene, 1,3-butadiene, 1,2-butadiene, and 1-butyne. The yield of carbon monoxide over oxygen atoms produced (φCO) was equal to the sum of the yields of C4H6 isomers in any experiment. φCO was 0.43 at the total pressure of 6.5 torr and 0.20 at 500 torr. We did not succeed in detecting any addition products such as C5H6O isomers.It was found that 3-methylcyclopropene was produced with excess energy and was partly isomerized to other C4H6 isomers, especially to 1-butyne. The excess energy was estimated to be about 50 kcal/mol.The rate coefficient of the reaction was obtained relative to those for the reactions of atomic oxygen with trans-2-butene and 1-butene. The ratios kCPD+O/ktrans-2-butene+O= 2.34 and kCPD+O/k1-butene+O = 11.3 were obtained.Probable reaction mechanisms and intermediates are suggested.
    Additional Material: 7 Ill.
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  • 172
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of chlorine atom abstraction from the chloroethanes (EClH) 1,1,2-C2Cl3H3, 1,1-C2Cl2H4, and 1,2-C2Cl2H4 by radiolytically generated cyclohexyl radicals was studied in the liquid phase by a competitive method. The chlorine atom abstraction data were put on an absolute basis by comparing the rates of the metathetical reactions with the known rate of addition of cyclohexyl radicals to C2Cl4. The following Arrhenius parameters were obtained: TextE(EClH)-TemperatureA(ECLH)E(CCl4)log A(EClH)E(EClH)RangelogEClHA(C2Cl4)(kcal/mol)(1.mol·sec)(kcal/mol)(°C)CHCL2CH2Cl0.03 ± 0.083.87 ± 0.178.98 ± 0.1411.17 ± 0.27150 - 250CHCL2CH30.13 ± 0.134.63 ± 0.278.18 ± 0.1911.93 ± 0.37130 - 250CHCL2CH2Cl0.50 ± 0.177.57 ± 0.359.18 ± 0.2314.87 ± 0.45150 - 250The error limits are the standard deviations from least mean square Arrhenius plots.The α and ß activation effects on the kinetics of Cl atom abstraction from chloroalkanes are discussed. From the linear relation between the relative reactivities of cyclohexyl radicals toward the XCCl3 and XCHCl2 series, ECl(c-C6H11· + CHCl2CHCl2) = 10.2 ± 1 kcal/mol and ECl(c-C6H11· + CHCl22CCl3) = 9.7 ± 1 kcal is derived.
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  • 173
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    International Journal of Chemical Kinetics 9 (1977), S. 111-122 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of OH(v = 1) with HBr, O, and CO have been studied at 295°K using a fast discharge flow apparatus: The reaction O + HBr → OH(v = 1) + Br was used as a source of OH(v = 1), and subsequent chemical reactions of the excited radical were followed using EPR spectroscopy. Rate constants for reactions (2b), (3b), and (6b) were measured as (4.5 ± 1.3) × 10-11, (10.5 ± 5.3) × 10-11, and 〈5 × 10-12 cm3/molec·sec, respectively. The rate constant for physical deactivation of OH(v = 1) by CO was determined as 〈4 × 10-13 cm3/molec·sec.
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  • 174
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    International Journal of Chemical Kinetics 9 (1977) 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 175
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    International Journal of Chemical Kinetics 9 (1977), S. 185-200 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions have been studied by a mass-balance method involving the photolysis of small amounts of biacetyl in the presence of a large excess of isobutane containing a small proportion of the unsaturated substrate. The following Arrhenius parameters have been derived: TextTemperatureElog ArangeReaction(kcal/mol)(1./mol·sec)(°K)ĊH3 + C2H4 → Ċ3H77.3 ± 1.08.32 ± 0.5350 - 500ĊH3 + C2H2 → Ċ3H57.7 ± 1.58.79 ± 0.8379 - 487ĊH3 + C6H6 → C7H97.6 ± 1.08.79 ± 0.5372 - 484The results for methyl addition to ethylene are based on previous determinations by other techniques as well as the present studies. The results for methyl addition to acetylene and benzene are derived solely from the present experiments and are calculated relative to a rate constant of log k2(l./mol·sec) = 7.42 - (7.1/θ) for the reference reaction (2), ·H3 + (CH3)3CH → CH4 + ·4H9.
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  • 176
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    International Journal of Chemical Kinetics 9 (1977), S. 725-741 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of propene in the presence of D2 was studied in a single-pulse shock tube in the temperature range of 1200-1400°K. The main decomposition products were methane, ethylene, allene, and propyne. Furthermore, deuterated species were observed of each product and of propene, with characteristic compositions that were dependent on propene conversion. Geometrical isomers of monodeuterated propene, as the result of H-D exchange, were analyzed by microwave spectroscopy. From these observations, the reactivities of n- and isopropyl radicals at high temperatures were determined. The former was found to be an intermediate of methane and ethylene and the latter was found to be responsible for the formation of the deuterated propene as follows: The rate constant ratio kn/ki was estimated to be 0.5-0.8, which was more than ten times greater than that obtained at room temperature. It was also found that allene or propyne was produced from allyl radicals and that acetylene was produced from vinyl radicals. In addition, the rate constant of the hydrogen abstraction by the hydrogen atom from C3H6 was found to be six times greater than that by the hydrogen atom from D2.
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  • 177
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    International Journal of Chemical Kinetics 9 (1977), S. 841-862 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation of cerous ions by bromate ions in sulfuric acid medium was followed spectrophotometrically under various experimental conditions. The results were compared to the calculated predictions on the basis of a mechanism suggested by R. M. Noyes and collaborators. The computations were done by solving the complete set of the kinetic differential equations. The results of the computations show that the proposed mechanism explains adequately most of our and previous experimental data. In particular, the mechanism predicts the main features of the reaction, namely, the induction and the fast and slow reaction periods which occur during the oxidation.
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  • 178
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    International Journal of Chemical Kinetics 9 (1977), S. 887-905 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of NO2 and its atom-transfer reactions with SO2 and CO have been studied behind incident shock waves using photometric detection methods. From the decomposition study it is possible to obtain information on the rate of the reaction 2NO2 → antisymmetric-NO3 + NO. The results on the reaction, NO2 + SO2 → NO + SO3 extend the earlier work of Armitage and Cullis to about 2000°K. The reaction with CO [NO2 +] [CO NO + CO2] at shock temperatures is somewhat faster than predicted from available low-temperature data and provides a modification of the rate-constant expression that is applicable over a wide temperature range.
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  • 179
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    International Journal of Chemical Kinetics 9 (1977), S. 953-968 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reaction of cis-(NO)2 with solid oxygen to form iso-N2O4 have been studied between 13 and 29 K. The overall reaction is pseudo first order in cis-(NO)2, and solid oxygen serves both as a reactant and the matrix. The pseudo-first-order rate constants are calculated to be k(14N) = 4.25 × 10-2 exp(-103/RT), and k(15N) = 3.00 × 10-2 exp(-105/RT) sec-1, based on temperature measurements from a thermocouple junction which may be at most three degrees lower than the actual reacting film. Most significantly, however, 14k/15k = 1.55 at∼13 K. The condensed phase reaction has been compared to that observed in the gas phase, and the extremely small pre-exponential factors and large isotope effects have been discussed in terms of tunneling corrections and orientational constraints. It is suggested that the form of the crystal plays an integral role in the observed process.
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  • 180
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    International Journal of Chemical Kinetics 9 (1977), S. 179-184 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Computer calculations of the kinetics of the ferric ion catalyzed decomposition of H2O2 by Walling and Weil are not in contradiction to the “complex mechanism.” The examination of their results reveals that their simulations correspond to the terminal state of the system in which the secondary complex between Fe3+ and H2O2 becomes stabilized.
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  • 181
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    International Journal of Chemical Kinetics 9 (1977), S. 201-213 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unimolecular decomposition of chemically activated methylallylether (MAE) formed by the cross combination of methoxymethyl and vinyl radicals was studied in the gas phase. The experimentally determined rate constant was found to be 1.11 × 108 sec-1 at 9.6°C for the decomposition of MAE into propene and formaldehyde. The decomposition of MAE via the six-center retro-“ene” type transition state is analyzed by using the RRKM unimolecular reaction theory. For the molecular parameter assignments of energized MAE, a model which contains one internal rotational mode is supported, and MAE decomposition is characterized by a tight complex model. The best agreement between experimental and theoretical results was found when a critical energy of 40.1 kcal/mol was used.
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  • 182
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    International Journal of Chemical Kinetics 9 (1977), S. 267-282 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction H + CH3OOH was investigated under conditions of excess atomic hydrogen concentration using a flow reactor attached to a photoionization mass spectrometer. The rate coefficient of the reaction was determined as \documentclass{article}\pagestyle{empty}\begin{document}$$ k = (2.8 \pm 0.9) \times 10^{- 13} {\rm exp\,}[- (1860 \pm 190){\rm cal}/RT \cdot {\rm mol\,}]\,{\rm cm}^3 /{\rm molec} \cdot {\rm sec} $$\end{document} The three important reaction channels were found to be with the individual contributions determined as indicated. The product methoxy and methylperoxy radicals react mainly with atomic hydrogen under the employed experimental conditions according to where the estimates for the percentage contributions of the various channels were derived from the measured product yields.
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  • 183
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    International Journal of Chemical Kinetics 9 (1977), S. 317-317 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 184
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    International Journal of Chemical Kinetics 9 (1977), S. 387-398 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of modern theories of energy transfer to unimolecular reactions taking place at very high temperatures is discussed. It is shown that the efficiency of energy transfer for both reactant-reactant and reactant-inert diluent collisions may be substantially smaller than the values determined experimentally at lower temperatures. Consequently at high temperatures unimolecular falloff effects, particularly in some shock-tube measurements, may be greater than has been believed hitherto.The application of these calculations to the unimolecular reactions of cyclopropane, cyclobutane, and cyclohexene at temperatures around 1300°K is discussed, and it is shown that under shock-tube conditions the apparent first-order rate coefficient may be at least ten times less than the high-pressure limiting value.
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  • 185
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    International Journal of Chemical Kinetics 9 (1977), S. 361-369 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the gamma radiation induced free radical chain decomposition of BrCH2CN in liquid cyclohexane (RH) was investigated over the temperature range of 60-170°C. In addition competitive experiments in the presence of CCl4 were carried out between 80 and 180°C. For the reactions the following Arrhenius expressions were derived: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} {\rm log}k_3 /(2k_4)^{1/2} ({\rm l}^{{\rm 1/2}} /({\rm mol} \cdot {\rm sec})^{1/2}) = 4.07 \pm 0.35 - (11.96 \pm 0.63)/\theta \\ {\rm log}k_2 /k_5 = - 0.699 \pm 0.167) + (2.69 \pm 0.31)/\theta \\ \end{array} $$\end{document} where θ = 2.303RT in kcal/mol.The effect of CN substitution on the activation energies of reactions (2) and (3) was evaluated based on the present and previously published results. The CN group effect on halogen atom abstraction [reaction (2)] is discussed in terms of inductive and enthalpic factors.The differences E3 - E(CH3 + RH) and E(CCl2CN + RH) - E(CCl3 + RH), which yield a value of about 5.5 kcal/mol, are considered to reflect the cyano stabilization effect at the radical center confirming D(CH2(CN)-H) ∼ 93 kcal/mol.
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  • 186
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    International Journal of Chemical Kinetics 9 (1977), S. 399-407 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nanosecond flash photolysis of 1,2- and 1,8-dinitronaphthalenes (1,2-DNO2N; 1,8-DNO2N) in nonpolar and polar solvents shows transient species with absorption maxima and lifetimes dependent on solvent polarity. In deaerated n-hexane the absorption maxima and lifetimes (1/K) are 490 nm and 1.0 μsec for 1,2-DNO2N and 550 nm and 2.5 μsec for 1,8-DNO2N. In deaerated ethanol the corresponding values are 550 nm and 4.3 μsec for 1,2-DNO2N and 590 nm and 5.3 μsec for 1,8-DNO2N. The transient absorptions are attributed to the lowest triplet excited states T1 of the 1,2- and 1,8-DNO2N. The observed red shifts in the absorption maxima of the T1 states are indicative of the extent to which electronic charge is transferred intramolecularly during the T1 → Tn transitions. Furthermore, the increased lifetime of the T1 states with increasing solvent polarity indicates the intramolecular charge transfer character of the T1 states. Changes of dipole moments accompanying the T1 → Tn transitions as well as rate constants for electron or proton transfer and hydrogen abstraction reactions involving the T1 states of 1,2- and 1,8-DNO2N and tributyl tin hydride (Bu3SnH) as the hydrogen donor were determined together with the activation energy of the hydrogen abstraction reaction for the case of 1,2-DNO2N. The spectroscopic and kinetic data obtained in this work demonstrate that the triplet states of 1,2- and 1,8-DNO2N behave like n → π* states in nonpolar media while in polar solvents the n → π* character of these states is reduced with a simultaneous increase in their intramolecular charge transfer character.
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  • 187
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    International Journal of Chemical Kinetics 9 (1977), S. 451-469 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the technique of molecular modulation spectrometry, we have measured directly the rate constants of several reactions involved in the oxidation of methyl radicals at room temperature: k1 is in the fall-off pressure regime at our experimental pressures (20-760 torr) where the order lies between second and third and we obtain an estimate for the second-orderlimit of (1.2 ± 0.6) × 10-12 cm3/molec · sec, together with third-order rate constants of (3.1 ± 0.8) × 10-31 cm6/molec2 · sec with N2 as third body and (1.5 ± 0.8) × 10-30 with neopentane; we cannot differentiate between k2a and k2c and we conclude k2a + (k2c) = (3.05 ± 0.8) × 10-13 cm3/molec · sec and k2b = (1.6 ± 0.4) × 10-13 cm3/molec · sec; k3 = (6.0 ± 1.0) × 10-11 cm3/molec · sec.
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  • 188
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    International Journal of Chemical Kinetics 9 (1977), S. 489-501 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions between SO2 and O2 were carried out in the presence of TiO2 and NiO under various partial pressures of SO2 and O2 at temperatures from 240 to 330°C. TiO2 and NiO were pretreated by applying an annealing effect from which the catalysts would have the different activity. The rates are the highest for TiO2 pretreated at high temperature in the region of 400 to 600deg;C in vacuum, 1.21 × 10-4 mmHg. In contrast, the rates are the lowest for NiO pretreated at high temperaturefrom 350 to 550°C. The data have been correlated with 1.4 and first-order kinetics for TiO2 and NiO, respectively. A reaction mechanism to explain the data was suggested.The quantities of anionic vacancies in TiO2 surfaces and of positive holes in NiO appeared to be paramount in determining the type of kinetics.
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  • 189
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    International Journal of Chemical Kinetics 9 (1977), S. 535-548 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The general problem of eliciting reliable rate constants from experimental data is considered in detail for consecutive reactions. Practical aspects are emphasized.
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  • 190
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    International Journal of Chemical Kinetics 9 (1977), S. 619-628 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The room temperature photolysis of 1,1-dichloroethane at 147 nm in the pressure range of 1.34-196.2 torr is characterized almost entirely by the molecular elimination of HCl, Cl2, and small quantities of H2. Acetylene is also produced. While it is possible that the C2H2 arises, in part, from the decomposition of vibrationally excited ground states of C2H3Cl and/or C2H4, in this particlar case serious consideration has to be given to alternative explanations where the products of the primary processes are formed in electronically excited states. The ±, elimination of molecular chlorine is not inconsistent with an increased degree of Cl—Cl interaction predicted for a «Rydberg «state of 1,1-C2H4Cl2. Varying small yields of CH4 are observed in the presence and absence of NO. The effect of large pressures of CF4 on the quantum yields of the major products is extremely small. The extinction coefficient for 1,1-C2H4Cl2 at 147 nm and 296°K is 246 ± 29 cm-1 ± atm-1.
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  • 191
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    International Journal of Chemical Kinetics 9 (1977), S. 693-696 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NO Abstract.
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  • 192
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    International Journal of Chemical Kinetics 9 (1977), S. 743-749 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2-Fluorochloroethane was photolyzed at 147 nm in the pressure range of 3.8-20.9 torr. The effects of added NO, H2S, and large pressures of CF4 were also investigated. The exponential extinction coefficient at 147 nm and 296°K was found to be 147 ± 4 atm-1 · cm-1.The photochemistry in some respects is similar to that of ethyl chloride. The primary processes again appear to involve at least two excited states. One of these yields ethylene by FCl elimination (Φ ≃ 0.3) and has a lifetime of ∼3.2 × 10-10 sec, with respect to an internal conversion to the vibrationally excited ground state or, more probably, a collisionally induced crossover to a state decomposing mainly by carbon—halogen bond fission. The molecular elimination of HCl, H2, and small amounts of HF also occurs but not apparently from the same state as does FCl. The quantum yields of products with radical precursors, however, are not large, and hence little, if any, of the FCl and probably none of HCl, H2, and HF subsequently dissociates. The vinyl fluoride and vinyl chloride, accompanying the elimination of HF and HCl, are postulated as possible sources of the secondary production of acetylene.
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  • 193
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    International Journal of Chemical Kinetics 9 (1977) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 194
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron pulse radiolysis at ⋍298°K of 2 atm H2 containing 5 torr O2 produces HO2 free radical whose disappearance by reaction (1), HO2 + HO2 →H2O2 + O2, is monitored by kinetic spectrophotometry at 230.5 nm. Using a literature value for the HO2 absorption cross section, the values k1 = 2.5×10-12 cm3/molec·sec, which is in reasonable agreement with two earlier studies, and G(H) G(HO2) ⋍13 are obtained. In the presence of small amounts of added H2O or NH3, the observed second-order decay rate of the HO2 signal is found to increase by up to a factor of ⋍2.5. A proposed kinetic model quantitatively explains these data in terms of the formation of previously unpostulated 1:1 complexes, HO2 + H2O ⇋ HO2·H2O (4a) and HO2 + NH3⇋ HO2·NH3 (4b), which are more reactive than uncomplexed HO2 toward a second uncomplexed HO2 radical. The following equilibrium constants, which agree with independent theoretical calculations on these complexes, are derived from the data: 2×10-20≲K4a≲6.3 × 10-19 cm3/molec at 295°K and K4b = 3.4 × 10-18 cm3/molec at 298°K. Several deuterium isotope effects are also reported, including kH/kD = 2.8 for reaction (1). The atmospheric significance of these results is pointed out.
    Additional Material: 5 Ill.
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  • 195
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    International Journal of Chemical Kinetics 9 (1977), S. 929-941 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants have been estimated as a function of temperature for seven reactions of the type W + XYZ = WX + YZ, where W, X, Y, and Z are H and O atoms. From transition state theory and estimates of the heat capacities of activation, \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm int\, k/[cm}^{\rm 3} {\rm (mol} \cdot {\rm sec)] = 10}^{{\rm 15}{\rm .87}} \exp (\Delta S_{298}^{\circ _ \ne} /R)T^{0.75} \exp [- (\Delta H_{298}^{\circ _ \ne} + 0.74)/RT] $$\end{document} where int k is the rate constant per transferable atom for the forward and reverse reactions in the exothermic direction, and where ΔH°≠298 is in kcal/mol. Values of ΔS°≠298 and ΔH°≠298 were obtained from the above equation and previously measured and evaluated rate constants at 298°K. The results are summarized in a table. Rate constants were calculated at temperature from 250 to 2000 K. The estimated rate constants were compared with recommended values. The results for ΔH°≠298 for reactions (15), (16), (17), and (19), in which a stable intermediate may precede the transition state, together with similar results previously found for reactions X + YZ = XY + Z, suggests that many such reactions may have values of ΔH°≠298 that are close to zero. The result for the reaction O + O3 = O2 + O2 is however, an exception to the foregoing perhaps because it is the reaction of a singlet with a triplet.ΔS°≠298 for the same reaction is unexpectedly low.
    Additional Material: 7 Ill.
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  • 196
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    International Journal of Chemical Kinetics 9 (1977), S. 339-347 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the gas-phase thermal decomposition of 1,1,2-trifluoro-2-trifluoromethyl-cyclopropane to 2,3,3,3-tetrafluoropropene and CF2 was studied in the temperature range of 539-604°K and with a total pressure of 17 to 300 torr of a 1:20 mixture of reactant and perfluoroethylene. Some runs were also made with the reactant only, with initial pressures of 0.2 to 20 torr. The reaction is first order, homogeneous, and the rate constants fit the following Arrhenius relationship: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\,k/{\rm sec}^{- 1}) = (15.23 \pm 0.12) - (50,557 \pm 1100)/4.576T $$\end{document} .
    Additional Material: 2 Ill.
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  • 197
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    International Journal of Chemical Kinetics 9 (1977), S. 349-359 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal and methyl radical initiated decomposition of biacetyl-d6 were investigated at conversions 5% over the temperature range of 387-412°C and 251-292°C, respectively. The deuterated sample contained 10.5% biacetyl-d5. The reaction products were analyzed by mass spectrometry.The following data could be determined from product ratios: where E is in kcal/molWith reasonable assumptions and literature data Arrhenius parameters for elementary steps were derived and discussed in particular with respect to isotopic effects in H/D-abstraction reactions.
    Additional Material: 3 Ill.
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  • 198
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    International Journal of Chemical Kinetics 9 (1977), S. 417-423 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants for hydrogen transfer reactions from C - H bonds to O(3P) in the gas phase have been calculated by the bond-energy bond-order method. The use of a single or double triplet repulsion term is discussed. Computational results indicate that with carefully selected input parameters, it is unnecessary to use a double-repulsion term. Tunneling corrections were carried out by two different procedures. Results indicate that in this case there is not much difference between the simple Wigner's treatment and more complicated methods.
    Additional Material: 2 Tab.
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  • 199
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    International Journal of Chemical Kinetics 9 (1977), S. 481-488 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Arrhenius parameters are frequently evaluated incorrectly by applying the least squares method to the logarithmic form of the Arrhenius equation without simultaneously transforming the statistical weights as required for the change of variable from k to ln k. This has been mentioned briefly in an earlier paper. In the present communication the correct procedures are discussed and illustrated by several examples of evaluations. In particular, Arrhenius parameters calculated by the Taylor series expansion of the exponential form of the Arrhenius equation are compared with those calculated from the logarithmic form, using an exact and two approximate transformations of the statistical weights. The comparisons indicate thatthe preferred procedure for obtaining Arrhenius parameters is either the Taylor series method or the logarithmic method with proper transformation of the experimentally determined statistical weights of the rate constants ki. The common approximation of assuming equal statistical weights of ln ki when the logarithmic form of the Arrhenius expression is used is shown not to be always appropriate, and reasons forthis are given.
    Additional Material: 2 Tab.
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  • 200
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    International Journal of Chemical Kinetics 9 (1977), S. 507-509 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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