Reactions of carbonyl compounds in basic solutions. Part 18. The mechanisms of the alkaline hydrolysis of methyl benzil-2-carboxylates and 2-phenylacetylbenzoates

Abstract

Rate coefficients have been measured for the alkaline hydrolysis of methyl 3′- and 4′-substituted benzil-2-carboxylates at 21.0 °C and methyl 2-(3- and 4-substituied phenylacetyl)benzoates at 24.0 °C in 70%(V/V) dioxane–water. Those for the two parent esters were also measured at several temperatures and the enthalpies and entropies of activation have been evaluated. The relative rates of hydrolysis, activation parameters and substituent effects have been used to demonstrate neighbouring group participation by keto-carbonyl groups in the alkaline hydrolysis of the esters under study. For the methyl benzil-2-carboxylates, the α-carbonyl group appears to participate by means of an intermediate having a five-membered ring.