Correlation analysis of reactivity in the addition of substituted benzylamines to benzylidenemalononitrile

The kinetics of addition of a number of ortho-, meta-, and para-substituted benzylamines to benzylidenemalononitrile (BMN) in acetonitrile have been studied. The reaction is first-order with respect to BMN. The order with respect to the amine is more than one. It has been shown that the reaction followed two mechanistic pathways, uncatalyzed and catalyzed by the amine. The enthalpy of activation for the catalyzed path is negative indicating the presence of a preequilibrium (k1, k−1) leading to the formation of a zwitterion. The values of rate constant, k1, for the nucleophilic attack have been determined for twenty-eight benzylamines. The rate constant, k1 was subjected to correlation analyses using various single- and multi-parametric equations. The best correlation is obtained in terms of Charton's LDR and LDRS equations. The polar regression coefficients are negative indicating the formation of a cationic species in the transition state. The reaction is subject to steric hindrance by ortho-substituents.