Solvolysis reactions of some substituted benzoyl chlorides were studied in ethanol-water, ethanol-trifluoroethanol and methanol-acetonitrile mixtures. Results showed that the reaction proceeds via an $S_N2$ process in which bond formation is more advanced than bond cleavage. Comparison of the two models for predicting transition state variation indicated superior nature of the quantum mechanical model relative to the potential energy surface model.