Kinetics of the alkaline hydrolysis of several alkyl phenylcarbazates

Abstract

The kinetics in 25%(v/v) dioxane–water of the alkaline hydrolysis, followed by UV spectrometry, of several alkyl phenylcarbazates (Ar–NH–NHCOOR, with Ar = phenyl, 4-chlorophenyl, 4-fluorophenyl, 3,4-dichlorophenyl and R = methyl, ethyl, propyl, chloroethyl, trichloroethyl) are discussed. The pK_a of trichloroethyl phenylcarbazate is 14.12 at 25 °C. The pH profiles, the activation entropy of –40 cal mol^–1 K^–1, the kinetic solvent isotope effect, k_OH^–/k_OD^–, of 3.45, the general-base catalysis and the effect of the leaving group and of the substituent on the aromatic ring are in agreement with the involvement of a B_AC2 reaction scheme.