Kinetics and Mechanism of the Aminolysis of phenyl Cyclobutanecarboxylates in Acetonitrile

초록

Kinetic studies of the reaction of Z-phenylcyclobutane carboxylates with X-benzylamines in acetonitrile at 55.0 oC were carried out. The reaction proceeds by the stepwise mechanism in which the rate determining step is the breakdown of the zwitterionic tetrahedral intermediate, T+_, with a hydrogen-bonded four-center type transition state (TS). This mechanistic conclusions are drawn based on (i) the large magnituded of low X and low Z (ii) the normal kinetic isotope effects (kH/kD > 1.0) involving deuterated benzylamines, (iii) small positive enthalpy of activation, deta H#, and large negative entropy of activation, deta S#, (iv) the sign of low XZ is positive and the magnitude of low XZ is greater than for normal SN2 processes.