The kinetics of decarboxylation of benzoylacetic acid and its p-methoxy and p-nitro derivatives in dioxan-water mixtures

Abstract

The kinetics of the decarboxylation of benzoylacetic, p-nitrobenzoylacetic, and p-methoxybenzoylacetic acids and their anions, have been studied in 50/50 v/v dioxan-water at I 0.20M over a range of temperatures. Substituents in the aromatic ring have little or no effect on the relative rates of decarboxylation of the free acids. Values of ΔH? and ΔS? are the same within experimental error. Apparently polar effects are "swamped" by the polarization effect of the proton either partly or fully transferred to the carbonyl group. Polarization effects of this type do not occur with the anions and the expected substituent effects are observed, thus at 35.6º the relative rates are p-NO₂ (16) > pH (1) > p-OMe (0.26).