Non-linear structure-reactivity correlation in the addition reaction of <i>n- </i> butylamine to <i>para-</i> substitutedethyl <i>α</i>-cyanocinnamates

Abstract

The study of kinetics of addition of <i>n</i>-butylamine to a number of <i>para-</i> substitutedethyl a-cyanocinnamates in acetonitrile reveals that the reaction is first order in the substrate and the order In nucleophile varies with the nature of the <i>para</i>-substituent. The analysis of the rate data of the various <i>para-</i> substituted ethyl <i>α</i>-cyanocinnamates in terms of the Hammett equation gives a non-linear concavedown type of curve. A stepwise mechanism involving the formation of zwitterionic addition complex in an equilibrium step followed by conversion into the reaction product <i>via </i> a proton transfer In two routes, viz., non-catalytic and by amine catalysed, has been proposed. The non-linear structure-reactivity correlation has been accounted for by the change in rate-controlling step.