摘要:

AbstractA detailed kinetic study of the Mn(II)‐catalyzed and ‐uncatalyzed oxidation of pinacol by bromate has been carried out in aqueous acetic acid media containing Hg(II) ions. The uncatalyzed reaction exhibits 1.5 order that is, 0.5 order in [pinacol] and 1.0 in [bromate]. A decrease ink1by increasing [bromate] has been accounted for due to the formation of Br2O5, which is inactive toward reduction. Mn(II)‐catalyzed oxidation follows first order in [oxidant], 0.5 order in [manganous ion], and variable order with respect to [pinacol]. At lower [pinacol](0.005–0.025M) the order is 0.5, but at higher concentration (0.03–0.15M) it becomes negative (−1.0). These observations can be accounted for qualitatively by the formation of 1:1 and 1:2 Mn(II)–pinacol complexes of which only 1:1 is active toward bromate oxidation. At higher [pinacol] the ratio of 1:2 and 1:1 complexes reached 98.2. All reactions were accelerated with acidity, and the rate constant follows theh0function. Participation of H2O in the rate‐limiting step and a free‐radical mechanism were proposed for the manganous‐ion‐catalyzed reaction, whereas for the uncatalyzed reaction this was not true. The effects of NaClO4, Na4P2O7, and the dielectric constant of the media are also in accordance with t

ISSN:0538-8066    

DOI:10.1002/kin.550150402

出版商:John Wiley&Sons, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe kinetics of the oxidation of hydrogen iodide (HI + O2) at low temperature (414–499 K) in the gas phase by the method of iodination kinetics is complicated by a heterogeneous reaction between hydrogen iodide and oxygen. Present work leads to an upper limit for the bimolecular rate constantk1for the first and rate‐determining stepThese data are combined with an estimatedAfactorA1= 109.3±0.2L/mol·s (assuming a tight linear I···H···O— transition state), to calculate the lower limit of the activation energy for the forward reactionE1. This leads to a minimum value for the heat of formation of the HO2radical, ΔHf298°(HO

ISSN:0538-8066    

DOI:10.1002/kin.550150403

出版商:John Wiley&Sons, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractUsing currently available thermochemical and kinetic data and estimation methods to analyze the thermochemistry and the kinetic parameters of the elementary reactions involved in the oxidation of HCl and HBr, reaction mechanisms are proposed which account for the previously reported reaction products, the rate law, and the kinetic data. For oxidation of HCl, two competitive pathways, the radical initiation by hydrogen abstraction and the fourcenter reaction pathway, were invoked to account for the observations. In the oxidation of HBr one must invoke a fast surface reaction of the type\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm H}_2 {\rm O}_2 + {\rm HBr}({\rm S}) \to 2{\rm H}_2 {\rm O} + {\rm Br}_2 ({\rm g}) $$\end{document}to account for the reaction.

ISSN:0538-8066    

DOI:10.1002/kin.550150404

出版商:John Wiley&Sons, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThis investigation of the kinetics and thermodynamics of the thermal isomerization reaction of 1α,25‐dihydroxycholecalciferol, the physiologically active metabolite of vitamin D3, is based on the simultaneous determinations of 1α,25‐(OH)2D3and its previtamin analog by nuclear magnetic resonance spectroscopy which distinguishes these compounds from possible impurities. The kinetics at different temperatures are used to obtain the activation parameters for the sigmatropic [1,7] thermal interconversion process which is shown to be compatible with a reaction that is unimolecular and concerted. The nature of the transition state of the activated complex, the reaction energetics, and the relative stabilities of 1α,25‐(OH)2D3and vitamin D3are d

ISSN:0538-8066    

DOI:10.1002/kin.550150405

出版商:John Wiley&Sons, Inc.    

年代:1983

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550150401

出版商:John Wiley&Sons, Inc.    

年代:1983

数据来源: WILEY