Kinetics and mechanism of the aminolysis of O-ethyl S-aryl thiocarbonates in acetonitrile

Abstract

The kinetics and mechanism of the reactions of O-ethyl S-(Z)aryl thiocarbonates with (X)benzylamines in acetonitrile at 45.0 degrees C are studied. Relatively small values of beta(X) (beta(nuc)) = 0.6 similar to 0.8 and beta(Z) (beta(Ig)) = -0.5 similar to -0.7 together with a negative cross-interaction constant rho(XZ) (= -0.47) and failure of the reactivity-selectivity principle (RSP) are interpreted to indicate a concerted mechanism. The normal kinetic isotope effects (k(H)/k(D) = 1.3 similar to 1.8) involving deuterated benzylamine nucleophiles suggest a hydrogen-bonded, four-center-type transition state. (C) 2000 John Wiley & Sons, Inc.