| Abstrakt: |
The second-order rate constants k for the alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-CHCOCH, in aqueous 50.9% acetonitrile have been measured spectrophotometrically at 25°C. The log k values for meta and para derivatives correlated well with the Hammett σ substituent constants. The log k values for ortho-substituted phenyl benzoates showed good correlations with the Charton equation, containing the inductive, σ, resonance, σ, and steric, E, and Charton υ substituent constants. For ortho derivatives the predicted (log k) values were calculated with equation (log k) = (log k) + 0.059 + 2.19σ + 0.304σ + 2.79 E − 0.0164Δ Eσ - 0.0854Δ Eσ, where D E is the solvent electrophilicity, Δ E = E - E = −5.84 for aqueous 50.9% acetonitrile. The predicted (log k) values for phenyl ortho-, meta- and para-substituted benzoates in aqueous 50.9% acetonitrile at 25°C precisely coincided with the experimental log k values determined in the present work. The substituent effects from the benzoyl moiety and aryl moiety were compared by correlating the log k values for the alkaline hydrolysis of phenyl esters of substituted benzoic acids, X-CHCOCH, in various media with the corresponding log k values for substituted phenyl benzoates, CHCOCH-X. [ABSTRACT FROM AUTHOR] |
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