AbstractHydrolysis 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 part