Kinetic studies of hydrolysis of some alkyl benzenesulfinates^†

Hydrolysis reactions of methyl, ethyl, isopropyl, and t-butyl benzenesulfinates were kinetically investigated. Rates of alkaline hydrolysis decrease with increasing steric effects (Me > Et > i-Pr > t-Bu), while the t-butyl ester is the most reactive in perchloric acid (t-Bu > Me > Et > i-Pr). The hydrolysis is faster in HCl and HBr than in HClO₄, and the relative rates in the halide acids are not unusual (Me > Et > i-Pr ∼ t-Bu). The high reactivity of the t-butyl ester in HClO₄, is ascribed to the reaction at the carbon via the A1 mechanism, while halide ions accelerate the hydrolysis by nucleophilic participation at sulfur.