Reactions of carbonyl compounds in basic solutions. Part 21. The mechanisms of the alkaline hydrolysis of substituted methyl 2-(2-oxopropyl)- and 2-(2-oxo-2-phenylethyl)-benzoates and 2-(2-acetylphenyl)- and 2-(2-benzoylphenyl)-acetates.

Abstract

Rate coefficients have been measured for the alkaline hydrolysis of methyl 2-[2-oxa-2-(3- or 4-substituted phenyl)ethyl]benzoates, 2-[2-(3- or 4-substituted benzoyl)phenyl]acetates, 2-(2-oxopropyl) and 2-(1,1-dimethyl-2-oxopropyl)benzoates, 2-(2-acetylphenyl)acetate and 2-(2-acetylphenyl)-2,2-dimethylacetates in 70%(v/v) dioxane–water at 30.0 °C. Those for the six parent esters were also measured at 45.0 and 60.0 °C 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 participation by the keto-carbonyl groups in the alkaline hydrolysis of the esters under study. For comparable systems, participation by six-membered ring intermediates appears somewhat less advantageous than five-membered.