The rates of neutral hydrolysis of a series of 4-substituted benzyl trifluoroacetates 4-X-C6H4CH2OCOCF3, X = NO2, Cl, H, CH3, and OCH3have been studied in water and deuterium oxide, both solvents containing 0.012 mol fraction of acetone. The alteration of the rates with the nature of the 4-substituent and the kinetic solvent isotope effect (k(H2O)/k(D2O)) are consistent with the proposal that the esters with X = NO2, Cl, H, and CH3all react by an acyl–oxygen BAc2 mechanism. On the other hand, the same mechanistic criteria indicate that the 4-methoxybenzyl ester reacts by both the BAc2 and the SN1 alkyl–oxygen fission paths in equal amounts.