Reactions of carbonyl compounds in basic solutions. Part II. The mechanism of the alkaline hydrolysis of methyl 2-benzoylbenzoates

Abstract

Rate coefficients have been measured for the alkaline hydrolysis of methyl 3′- and 4′-substituted 2-benzoylbenzoates in 70%(v/v) dioxan–water at 30 °C. The pK_a values of the corresponding acids have been measured in 80%(w/w) 2-methoxyethanol–water at 25 °C. The effects of substitution have been assessed by means of the Hammett equation. Comparison of the reaction constants obtained with those for the reference systems, benzoic acids and their methyl esters, indicates clearly that, in the alkaline hydrolysis of the methyl 2-benzoylbenzoates, the rate-determining step involves direct or pre-equilibrium attack at the keto-carbonyl group.