Understanding Solvent Effects in the Solvolyses of 4-Fluorophenyl Chlorothionoformate.

The solvolyses of 4-fluorophenyl chlorothionoformate (1) are studied in fifteen binary aqueous organic mixtures of widely varying nucleophilicity and ionizing power values. The specific rates of solvolyses of 1 are plotted against the specific rates of solvolysis observed for phenyl chloroformate (2) and deviations from the line-of-best-fit are observed in some of the highly ionizing aqueous fluoroalcohol mixtures. An analysis of the solvolytic data accumulated using the extended (two-term) Grunwald-Winstein equation confirms this deviant behavior and shows that dual bimolecular addition-elimination and unimolecular ionization channels occur in the solvolyses of 1.