1992 Volume 65 Issue 4 Pages 1096-1100
The kinetics of oxidation of several substituted ethyl phenylthioacetates by bromamine-B (sodium salt of N-bromobenzenesulfonamide) has been studied in 50% (v/v) aqueous ethanol medium. Disodium hydrogenphosphate and sodium dihydrogenphosphate buffer has been used. The reaction is of a total second order, first order each with respect to the reactants. A catalytic effect of mercury has been observed and the order with respect to Hg(II) is one. Electron-releasing substituents generally accelerate the rate while electron-withdrawing groups retard the rate. A good correlation is found to exist between log k2 and Hammett σ constants. Two mechanisms have been proposed, one in presence of Hg(II) and the other in the absence of Hg(II). In presence of Hg(II), rate = k[C1][H2OBr]+ and in the absence of Hg(II), rate = k[S] [H2OBr]+
Susceptibility of the reaction to the steric effect of ortho substituents, has been analyzed in the light of application of Taft’s steric energy relationships.
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