Sulfuryl transfer reactions solvent effects

The reactive species under acidic conditions is the neutral ester. This reaction is believed to proceed by transfer of the proton from the sulfuryl group to the leaving group, as in reactions of phosphate monoester monoanions. A reduced value for d a solvent deuterium isotope effect of 2.43 " are consistent with proton transfer to the leaving group in the transition state. The intermediacy of free SO3 in the acid hydrolysis is sometimes assumed, but has not been proven. 

---