NONLINEAR STRUCTURE-REACTIVITY CORRELATION IN THE ADDITION-REACTION OF N-BUTYLAMINE TO PARASUBSTITUTED ETHYL ALPHA-CYANOCINNAMATES

The study of kinetics of addition of n-butylamine to a number of para- substituted ethyl alpha-cyanocinnamates in acetonitrile reveals that t he reaction is first order in the substrate and the order in nucleophi le varies with the nature of the para-substituent. The analysis of the rate data of the various parasubstituted ethyl alpha-cyanocinnamates in terms of the Hammett equation gives a non-linear concave-down type of curve. A stepwise mechanism involving the formation of zwitterionic addition complex in an equilibrium step followed by conversion into t he reaction product via a proton transfer in two routes, viz., non-cat alytic and by amine catalysed, has been proposed. The non-linear struc ture-reactivity correlation has been accounted for by the change in ra te-controlling step.