Abstract

The reactions of a series of secondary alicyclic amines with the title substrates are subjected to a kinetic investigation in aqueous solution, 25 °C, ionic strength 0.2 M (maintained with KCl). Under amine excess pseudo-first-order rate coefficients (kobsd) are found. The plots of kobsd against concentration of free amine at constant pH are linear, with the slopes (kN) independent of pH. The Brönsted-type plots obtained (log kN vs amine pKa) for the aminolysis of both substrates are linear with the same slope, ? = 0.26. From this value, the kinetic law, and the analysis of products, it is deduced that these reactions proceed through a zwitterionic tetrahedral addition intermediate (T±) on the reaction path, and its formation is the rate-determining step. From a comparison of the present reactions with the concerted aminolysis of substituted phenyl chloroformates in acetonitrile it is inferred that the change of S- by O- in T± and that of water by acetonitrile as solvent destabilizes T± in such a way that the stepwise reaction becomes enforced concerted.