Kinetics of hydrolysis of NN′-diarylsulphamides

The kinetics of hydrolysis of five para-substituted NN′-diarylsulphamides, p-XC₆H₄NHSO₂NHC₆H₄X-p (X = H, Me, MeO, Cl, or NO₂) in 9:1 v/v water-acetone containing added hydrochloric acid have been measured at 50 and 75°. The Hammett ρ for the hydrolysis reaction is +1.03. The effect on rate of varying the pH from 3.05 to 1.05 has been studied for both NN′-diphenylsulphamide and N-phenylsulphamic acid. The rate of hydrolysis of phenylsulphamic acid is ca. 100 times faster than the rate of hydrolysis of diphenylsulphamide under identical conditions. Thus the intermediacy of phenylsulphamate in the hydrolysis of diphenylsulphamide does not complicate the kinetics and first-order kinetics have been observed. The major hydrolytic pathway involves bimolecular water attack on unprotonated diarylsulphamide.