The separation of polar and steric effects in the reaction of ortho-substituted benzoate ions with ethyl bromoacetate

Abstract

The second-order rate coefficients for the reactions of ortho-substituted benzoate ions with ethyl bromo-acetate have been measured in a 90% acetone–10% water(v/v) mixture at three different temperatures and the results have been compared with those of phenacyl bromide. The order of reactivity ofortho- substituted benzoate ions with phenacyl bromide. Attempts have been made to analyse the rate data in terms of electronic and steric effects by employing Charton's treatment. Analysis of the results shows that the localized effect is predominant over the delocalized effect in each reaction series and electron-releasing groups favour the reaction and electron-withdrawing groups retard it. The steric term is rate accelerating. The ΔS‡ values for all the ortho-substituted benzoate ions are negative and it appears that the bulk effect of the substituent plays a part in the variation of ΔS‡.