Kinetic studies on the rearrangement of n-chloroacetanilide under pressure

Abstract

The rearrangement of N-chloroacetanilide was investigated at pressures of 1, 981, and 2059 atm. The reaction rates in aqueous solution were measured at 15, 25, and 35℃ in various hydrochloric acid concentrations. They gave ΔV≠value of about 5ml/mol and E_a of about 20kcal/mol at 1 atm. The reaction rates in aqueous ethanol solution offered the distance between two ions in the transition state. The distance was increased with increasing pressure from 2.6Å at 1 atm to 3.6Å at 2000 atm. From these evidences it seems that the activated complex in rate determining step is appreciably polar and solvated. The ratio of ortho- and para-chloroacetanilide is identical with the k_u/k_p ratio of chlorination of acetanilide. Dependencies of In (O)/(P) on pressure and temperature gave ΔV_o≠-ΔV_p≒ value of about 3ml and ∂E_II of 0.74 kcal/mol at 1 atm and suggested that the solvation change was an important factor for isomer distribution.