A Mechanistic Study for Aminolysis of p-Nitrophenyl Phenylacetate

Abstract

Second-order rate constants have been measured spectrophotometrically for the reactions of p-nitrophenyl phenylacetate (1) and benzoate (2) with a series of alicyclic amines in H 2O containing 20 mole % DMSO at 25.0°C. 1 appears to be more reactive than 2 toward all the amines studied, although phenylacetic acid is a weaker acid than benzoic acid. The higher reactivity of 1 can be attributed to resonance and/or steric effect, since the ground state of 2 can be stabilized by resonance and 1 would experience less steric hindrance due to the presence of CH 2 group between phenyl and C=O group. The reactivity of the amines increases with increasing their basicity. The Brönsted-type plots for aminolysis of 1 and 2 show good linearity with β nur values of 0.81 and 0.85, respectively, indicating that the TS structures of the aminolyses of 1 and 2 are similar. Besides, the linear Brönsted plots obtained in the present system clearly suggest that there is no mechanism change for the given series of the amines and the reactions of 1 and 2 proceed in a same mechanism.