Base-catalyzed Ring-opening Reactions of Epoxides

The effects of solvents, catalysts (C), and reaction temperature on the base-catalyzed ring-opening reactions of phenyl glycidyl ether (E) and substituted phenols or benzoic acids (P) have been examined to discuss the mechanism. "Termolecular complex mechanism" proposed previously by us were related to "simple ionic mechanism" as of old. The reactions of PGE and phenol in n-butanol using sodium phenolate as catalyst (it abbreviates to "in BuHO: φONa: φOH system") and in φNO2: NR3: φOH system follow the second-order kinetics: -dE/dt=-dP/dt=k3CE, Hammett's ρ-value about k3 is negative, and steric effects are scarcely observed. These results fit well to "simple ionic mechanism." But the reactions in xylene: NR3: φOH system, in φNO2: φONa: φOH system, in xylene: NR3: φCOOH sytsem and so on follow the third-order kinetics: -dE/dt=kcCPE, ρ-values about kc are positive, and steric effects of substituents or catalysts are clearly seen. Such results are not explained by "simple ionic mechanism", and "termolecular complex mechanism" becomes apposite. Which mechanism is operative is determined mainly by solvent, active hydrogen compound, and catalyst used.