摘要:

AbstractIt has been usually thought that the rate ofN‐Cl‐α‐amino acids decomposition changes and that their coefficient of molar absorptivity falls when pH2−; (ii) the effect of the method of mixing on the reaction rate; (iii) the absolute necessity of a very careful choice of buffers and solvents; and (iv) the need to check the accuracy of the mathematical model to describe the chemical processes. © 1993 Joh

ISSN:0538-8066    

DOI:10.1002/kin.550250502

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe photolysis ofN‐nitrosamines in solutions of acetonitrile follows a first‐order reaction with respect to the concentration of nitrosamine. Quantum yields are very low (≈ 0.1) and depend on the concentration of nitrosamine, with the observation of a linear correlation between the reciprocal of quantum yield and the reciprocal of nitrosamine concentration. For all the nitrosamines studied, the final product of the photolysis appears to be unique, alkylidenimine, which in the case of nitroso methyl benzyl amine undergoes a relatively rapid hydrolysis, giving rise to benzaldehyde, following second order kinetics. A provisional model consistent with the experimental results obtained in this work is proposed. © 1993 John Wiley&Son

ISSN:0538-8066    

DOI:10.1002/kin.550250503

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe hydrogen and chlorine atom abstraction reactions from CH3Cl by CF3radicals produced by the photolysis of hexafluoroacetone (HFA) and CF3I were studied relative to the recombination of CF3 radicals(I)The Arrhenius parameters obtained in the temperature range 416 to 578 K are:\documentclass{article}\pagestyle{empty}\begin{document}$$ Logk_3 /k_2^{1/2} [{\rm cm}^{3/2} {\rm mol}^{ - 1/2} s^{ - 1/2}] = (5.39 + 0.10) - (10490 + 150)/\theta $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ Logk_4 /k_2^{1/2} [{\rm cm}^{3/2} {\rm mol}^{ - 1/2} s^{ - 1/2}] = (4.52 + 0.11) - (13370 + 250)/\theta $$\end{document}where Θ = 2,303.RTcal mol−1andk2is the recombination rate constant for the CF3radicals.The factors that influence the transfer processes of chlorine and hydrogen are analyzed in a series of reactions of halomethanes with CF3and CH3radicals. © 1993 John Wiley&Sons,

ISSN:0538-8066    

DOI:10.1002/kin.550250504

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractA model based on the two film approximation is proposed for the description of the kinetics of the hydrogen isotope exchange between CHCl3and D2O. In this model, details of mass transfer in interfacial region between the two liquid phases are considered and the kinetics of the exchange reaction is quantitatively described without an adjusting parameter. This model is successful in explaining the experimental results obtained with high alkali concentrations, which has not been sufficiently explained in our previous article [M. Iwasaki et al.,J. Phys. Chem.,93,5139 (1989)]. © 1993 John Wiley&Sons, Inc

ISSN:0538-8066    

DOI:10.1002/kin.550250505

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe reaction of NO with O2has been investigated in aqueous solution. As demonstrated by ion chromatography, the sole product is NO2−. Kinetic studies of the reaction by stopped‐flow methods with absorbance and conductivity detection are in agreement that the rate law is ‐d[O2]/dt=k[NO]2[O2] withk= 2.1 × 106M−2s−1at 25°C. This rate law is unaffected by pH over the range from pH 1 to 13, and it holds with either NO or O2in excess. By studying the reaction over the temperature range from 10 to 40°C, the following activation parameters were obtained: ΔH≠= 4.6 ± 2.1 kJ mol−1and ΔS≠=−96 plusmn; 4 J K−1mol−1.

ISSN:0538-8066    

DOI:10.1002/kin.550250506

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractUsing the cyclic voltammetry (CV), the electron‐transfer kinetics for the reductions of NO+and NO2+cations have been studied at the Pt electrode in nitromethane, sulfolane, and propylene carbonate. The heterogeneous rate constants have been determined by two independent procedures from the transfer coefficient α, the diffusion coefficient D, from a detailed examination of the CV‐peak separations, and from an inspection of the values of the cathodic peak potentials at different scan rates. The results have been compared to those reported in the literature, and discussed. In the classical model, outer‐sphere electron‐transfer reactions are considered subject to an activation energy arising from solvent reorganization and bond reorganization processes. The solvent and molecular reorganizational barriers for these electroreductions have been assessed in aprotic media. The Marcus‐Hush theory has been applied to the self‐exchange reactions of the NO2+/NO2and NO+/NO couples in an attempt to predict the rate of electron transfer. The findings indicate some improvement between theory and experiment. However, it should be noted that the experimental values ofksfound for the NO2+reduction in the solvents used are still too high in comparison with those determined theoretically. In view of the fairly strong coordination of the solvent molecule(s) as ligand(s) to NO2+and NO+cations, we believe that such discrepancies should stem, to some extent, from the involvement of an inner‐sphere pathway by generation of an activated complex on the surface of the Pt electrode. © 1993 John

ISSN:0538-8066    

DOI:10.1002/kin.550250507

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe kinetics of the reaction of the benzyl radical with molecular oxygen has been studied between 393 and 433 K. The Discharge Flow technique with detection of benzyl radicals by Laser Induced Fluorescence in their visible absorption band has been used. All experiments have been performed at ≈1 torr in helium as the buffer gas. The radical benzyl decay plots are characteristic of the approach to equilibrium between benzyl and benzylperoxy: benzyl + O2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\longrightarrow\over {\smash{\longleftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} $\end{document}benzylperoxy (k3,k−3). Thanks to a reasonable assumption concerning the standard entropy of the reaction (3) (ΔS298°=−29 cal mol−1K−1), based on the additivity rules of Benson, the following reaction enthalpy is derived for reaction (3): ΔH298°=(−20 ± 1 kcal mol−1). This latter value is compared with a few enthalpies of other related reactions available in the literature. © 1993 J

ISSN:0538-8066    

DOI:10.1002/kin.550250508

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractKinetics of Nb(V) hydrolysis in MgCl2, Mg(ClO4)2mixtures has been investigated by electroanalytical methods and the rate constants determined. A hydrolysis model based on species postulated in the literature is proposed. Resolution of the corresponding differential equations led to results consistent with experimental data obtained from polarographic current vs. time curves. © 1993 John Wiley&Sons, Inc

ISSN:0538-8066    

DOI:10.1002/kin.550250509

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550250501

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY