In this study, we investigated the kinetics of the nucleophilic substitutions, RX + (BzBu(3)NBr) reversible arrow RBr + (BzBu(3)NX), where R = allyl, Bu and Bz, when X = CI; and X = AcO and BzO when R = Bz. The forward and backward rate constants in addition to the activation energies for R = allyl and Bu were also determined. However, only the rate constants at 35 degrees C were determined for the benzyl compounds with toluene as the solvent to reduce the reaction rate. Moreover, the effects of the structures of the groups R and the leaving groups X on the reactivity were compared. Results in this study can provide valuable information for future studies involving the phase transfer catalyzed displacements. (C) 1996 John Wiley & Sons, Inc.