Buffer Catalysis of the Hydrolysis of Phenyl and Methyl Benzenesulfinates. Contrasting Behavior between Acyclic and Cyclic Analogs

Article abstract of DOI:10.1246/bcsj.69.3281

The hydrolysis of phenyl benzenesulfinate is catalyzed by both acid and base, and is strongly accelerated by the carboxylate and amine base components of the buffer. Carboxylates and amines constitute different groups in the Bronsted plots, falling nearly on two separate lines of β=1. The carboxylates are about 400-times more effective catalysts than the amines of similar basicity. Solvent deuterium isotope effects on the catalytic constants are small, and the buffer catalysis is considered to be nucleophilic. By contrast, the hydrolysis of the methyl ester was only weakly affected by the buffer, if at all. High efficiencies of oxygen nucleophiles in the catalysis of the hydrolysis of acyclic sulfinates are distinctive compared with the cyclic analogs, and are rationalized by a concerted S_N2-like mechanism of the nucleophilic reaction at sulfur.