A MECHANISTIC STUDY FOR AMINOLYSIS OF P-NITROPHENYL PHENYLACETATE

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 H2O containing 20 mole % DMSO at 25.0 degrees C. 1 appears to be more reactive than 2 toward all the am ines studied, although phenylacetic acid is a weaker acid than benzoic acid. The higher reactivity of 1 can be attributed to resonance and/o r steric effect, since the ground state of 2 can be stabilized by reso nance and 1 would experience less steric hindrance due to the presence of CH2 group between phenyl and C=0 group. The reactivity of the amin es increases with increasing their basicity. The Bronsted-type plots f or aminolysis of 1 and 2 show good linearity with beta(nuc) 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 Bronsted plots obtained in the present system clearly suggest that there is no mechan ism change for the given series of the amines and the reactions of 1 a nd 2 proceed in a same mechanism.