Correlation of the Rates of Solvolysis of Phenyl Fluorothionoformate

Abstract

The specific rates of solvolysis of phenyl fluorothionoformate (PhOCSF, 1) have been determined in 22 pure and binary solvents at 10.0 ^oC. The extended Grunwald-Winstein equation has been applied to the specific rates of solvolysis of 1 over the full range of solvents. The sensitivities (l = 1.32 ± 0.13 and m = 0.39 ± 0.08) toward the changes in solvent nucleophilicity and solvent ionizing power, and the kF/kCl values are similar to those previously observed for solvolyses of acyl haloformate esters, consistent with the addition step of an additionelimination pathway being rate-determining. The large negative values for the entropies of activation are consistent with the bimolecular nature of the proposed rate-determining step. The results are compared with those reported earlier for phenyl chloroformate and chlorothionoformate esters and mechanistic conclusions are drawn.