Reactions of carbonyl compounds in basic solutions. Part V. The mechanism of the alkaline hydrolysis of methyl 8-(3- or 4-substituted benzoyl)-, 8-formyl-, and 8-pivaloyl-1-naphthoates and methyl 5-formylphenanthrene-4-carboxylate. Neighbouring-group participation by carbonyl groups

Abstract

Rate coefficients have been measured for the alkaline hydrolysis of methyl 8-formyl-, 8-(3- or 4-substituted benzoyl)-, and 8-pivaloyl-1-naphthoates and methyl 5-formylphenanthrene-4-carboxylate in 70%(v/v) dioxan–water at several temperatures. The entropies and enthalpies of activation have been evaluated. The effect of a series of 8-substituents on the alkaline hydrolysis of methyl 1-naphthoate has been examined. The relative rates of hydrolysis, activation parameters, substituent effects, and solvent isotope effects have been used to demonstrate the occurrence of neighbouring-group participation by the formyl- or benzoyl-carbonyl groups in the alkaline hydrolysis. The importance of proximity, orientation, and steric strain factors are discussed.