Reactivity of beta-aroylacrylic acids with diazodiphenylmethane

Abstract

The rate constants for 10 trans-substituted beta-aroylacrylic acids in their reaction with diazodiphenylmethane (DDM) were determined in ethanol at 30 degrees C. The intention was to study the transmission of electronic effects of substituents on the phenyl nuclei to the carboxylic group reaction center, through the -C(=O)-CH=CH-group. The obtained rate constants were analyzed with the classical Hammett equation and the extended Hammett and Taft equation. It was possible, using Taft's relationship, to effect the separation of the overall polar effect into inductive and resonance components. The pattern of transmission through the observed conjugated system has been discussed. Conformational variations caused by variable substituents in an aromatic ring were calculated using the MNDO-AM I semiempirical method. The inclusion of a calculated conformational effect considerably improves the regression.