A detailed mechanism for the oxidation of aryl sulfides by peroxymonocarbon
ate ion in cosolvent/water media is described. Kinetic studies were perform
ed to characterize the transition state, including a Hammett correlation an
d variation of solvent composition, The results are consistent with a charg
e-separated transition state relative to the reactants, with an increaser o
f positive charge on the sulfur following nucleophilic attack-of the sulfid
e at the electrophilic oxygen of peroxymonocarbonate. In addition, an avera
ge solvent isotope effect of 1.5 +/- 0.2 for most aryl sulfide oxidations i
s consistent with proton transfer in the transition state of the rate-deter
mining step. Activation parameters for oxidation of ethyl phenyl sulfide in
tert-butyl alcohol/water are;reported. From the pH dependence of oxidation
rates and C-13 NMR equilibrium experiments, the estimated pK(a) of peroxym
onocarbonate was found to be similar to 10.6.