C. SRINIVASAK, P. KUTHALIXCAM, and N. ARUMUGAM. Can. J. Chem. 56.3033 (1978). The kinetics of oxidation of a number of alkyl aryl sulfides with potassium peroxydisulfate in aqueous ethanol have been investigated. The effect of substituents on the oxidation has been studied by employing a number of p-and m-substituted phenyl methyl sulfides: the reaction is accelerated by electron-releasing and retarded by electron-withdrawing substituents, indicating a rate-determining electrophilic attack by the peroxydisulfate ion at the reaction site, sulfur. A good correlation is found to exist between the rate constants and the Hammett o+jo-constants, the p + value for the reaction being -0.56 with a correlation coefficient of 0.979. The activation parameters have also been determined.Studies with different alkyl phenyl sulfides clearly indicate that the reaction is quite sensitive to steric congestion around the reaction site. The results obtained in this study are cornpared with those found for the oxidation of the same set of sulfides with different oxidants. Des etudes sur differents sulfures d'alkyle et de phenyle nlontrent claireinent que la reaction est grandement influencee par I'encombrement sterique au voisinage du site reactionnel. On compare les resultats recueillis dans le prisent travail avec ceux qui ont ete rapportes pour l'oxydation de la menie serie de sulfures avec differents oxydants.[Traduit par le journal]
The kinetics of oxidation of some ortho-substituted N,N-dimethylanilines by peroxodisulphate have been studied in 50% (v/v) aqueous ethanol containing 0.025 mol dm-3 phosphate buffer (pH 7). The reaction is second-order overall, and first-order in each reactant. The rate is not influenced by the presence of the free-radical inhibitor allyl acetate. A n increase in the polarity of the medium enhances the rate. The reactivities of ortho-substituted anilines lie in the order o-H > M e -M e 0 > F > Br > CI > NO,. Multiple regression analysis of the rate data reveals that the rate is susceptible to significant electronic and steric effects. All these observations are rationalised on the basis of attack of the oxidant at the ipso-position of the amine. Correlation analysis of reactivity data from the literature also indicates that the mechanism involves ipso-attack and not attack on nitrogen.
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