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

Abstract

Rate constants are reported at 25 ºC for solvolyses of p-Z-substituted benzoyl chlorides (Z = O 2 N, Cl, H, Me, and MeO) in 2,2,2-trifluoroethanol (TFE) in binary mixtures with water or ethanol. Product selectivities (k TFE /k water ) 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.

Reaction Mechanism Studies Involving the Correlation of the Rates of Solvolysis of Benzoyl and P-Nitrobenzoyl P-Toluenesulfonates

“…Table 3 reports comparisons of the reported specific rates at 25.0 °C, or values obtained at 25.0 °C by use of the Arrhenius equation, with literature values for chlorides or fluorides. For 1, the comparison is with literature values for both chlorides [24][25][26][27][28][29] and fluorides 30 and, for 2, the values required for comparison are only available for chlorides. 24,28,[31][32][33] In Table 4, the specific rates of solvolysis in methanol (k H ) and methan(ol-d) (k D ) are compared at -10 °C for the methanolyses of both 1 and 2.…”