KINETICS OF THE ALKALINE-HYDROLYSIS OF SEVERAL ALKYL PHENYLCARBAZATES

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-degrees-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(Ac)2 reaction scheme.