The effects of substituents on the rate of saponification of biphenyl-4-carboxylates

Second-order rate constants have been measured for the saponification of methyl 2′-, 3′-, and 4′- substituted biphenyl-4-carboxylates at several temperatures in 85%(w/w) methanol–water and activation parameters have been calculated. The Hammett equation applies very well to the saponification of 3′-and 4′-substituted biphenyl-4-carboxylates with σ-constants evaluated by the FMMF method. The effect of 2′-substituents is understandable in terms of π-electron steric effects.