Concurrent pathways to explain solvent and substituent effects for solvolyses of benzoyl chlorides in ethanol-trifluoroethanol mixtures

Rate constants are reported at 25 oC for solvolyses of p-Z-substituted benzoyl chlorides (Z = O2N, Cl, H, Me, and MeO) in 2,2,2-trifluoroethanol (TFE) in binary mixtures with water or ethanol. Product selectivities (kTFE/kwater) are also reported. Previous work in which rate constants for solvolyses of benzoyl chlorides are correlated with σ constants is re-evaluated. V-shaped plots (assuming concurrent reactions) are constructed from logarithms of rate constants vs. σ (not σ ) for substituent effects or a suitable parameter for solvent effects. Conditions are established for which it is predicted that concurrent mechanisms (one dissociative, one associative) each contribute 50% towards the observed rate constants.