Kinetics of oxidation of some meta‐ and para‐substituted phenyl methyl sulfoxides by chloramine‐T in buffered ethanol–water

The kinetics of oxidation of methyl phenyl sulfoxide by chloramine‐T (CAT) has been studied in buffered ethanol–water (1:1 v/v) of pH 7.0. The reaction was found to follow no simple‐order kinetics. A possible mechanism is suggested involving three rate‐controlling steps: (1) the reaction between RNHCl (R = CH 3 C 6 H 4 SO 2 ) and the sulfoxide, (2) the disproportionation of RNHCl, and (3) the reaction between RNCl 2 and the sulfoxide. A mixed‐order rate law is derived as rate/[C][SO] = k 1 + K d k 2 [C]/[SA]. The rate law is found to be obeyed for the meta‐ and para‐substituted phenyl methyl sulfoxides also. The ρ value is obtained using Hammett's σ constants. The ρ values obtained for the attack of both RNHCl and RNCl 2 with the sulfoxides are almost the same, showing that both are converting the sulfoxide to the same intermediate. A chlorinium ion transfer is suggested.