Substituent effects in the hydrolysis of diazoacetophenone

Abstract

First-order rate constants for the acid catalysed hydrolysis of ω-diazoacetophenone and twelve meta- and para-substituted diazoacetophenones in a water–dioxan mixture have been measured at four different temperatures. Except for the p-methoxy- and p-ethoxy-derivatives the results at each temperature are well correlated by the Hammett substituent constants.

Experiments at intermediate temperatures did not support the temperature-dependence of some of the activation parameters indicated by preliminary experiments. Most of the compounds studied have approximately the same apparent enthalpy of activation. The apparent activation entropies are in the approximate range +9 to –6 cal.°K^–1. It is possible that a compensating relationship exists between ΔH* and ΔS* in the case of the meta-halogen-substituted diazoacetophenones studied.