摘要:

AbstractA method is described for the measurement of relative rate constants for abstraction of hydrogen from ethylene at temperatures in the region of 750 K. The method is based on the effect of the addition of small quantities of propane and isobutane on the rates of formation of products in the thermal chain reactions of ethylene. On the assumption that methane and ethane are formed by the following reactions,measurements of the ratio of the rates of formation of methane and ethane in the presence and absence of the additive gave the following results:\documentclass{article}\pagestyle{empty}\begin{document}$$\log (k_7 /k_2) = (- 0.50 \pm 0.4) + (3200 \pm 1000)/2.3T$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\log (k_8 /k_3) = (- 0.20 \pm 0.4) + (2800 \pm 1000)/2.3T$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\log (k_{11} /k_2) = (- 0.97 \pm 0.4) + (4600 \pm 1000)/2.3T$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$\log (k_{12} /k_3) = (- 2.0 \pm 0.4) + (6300 \pm 1000)/2.3T$$\end{document}Values fork2andk3obtained from these ratios are compared with previous measurements.

ISSN:0538-8066    

DOI:10.1002/kin.550210102

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractRate constants and activation parameters of direct reaction of oxirane with certain alkyl‐2‐hydroxyethyl sulfides and/or successive oxyethylene adducts in the presence of basic catalyst were studied at temperatures 323–353 K. The reactions were found to be of the first order with respect to oxirane, sulfide, and catalyst concentrations. The kinetics are consistent with a termolecular mech

ISSN:0538-8066    

DOI:10.1002/kin.550210103

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractKinetics 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 mec

ISSN:0538-8066    

DOI:10.1002/kin.550210104

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractWe have carried out a kinetic study of the 4‐pyridinecarboxaldehyde plusn‐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 pKais 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 nonprotonatedn‐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 separ

ISSN:0538-8066    

DOI:10.1002/kin.550210105

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550210101

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY