The hydrolysis of aryl N-(substituted phenylsulfonyl)carbamates at 50 degrees C in the pH range 0-13.5 leading to substituted benzenesulfonamides and phenols involves acyl group transfer. Reaction rates were measured spectrophotometrically and are independent of the concentration of the catalyst for buffers of pK(BH) > 8. With more acidic buffers, a general acid catalysis is observed for the hydrolysis of phenyl N-(phenylsulfonyl)carbamate la (pK, = 2.85) leading to a Bronsted relation (alpha = 0.46) including hydronium ion while it does not occur for 4-cyanophenyl N-(phenylsulfonyl)carbamate 1d. In alkaline media, the values of the entropies of activation are positive and lie between 0.20 and 15.0 cal mol(-1) K-1. The Hammett rho(-) value for the expulsion rate k(p) of phenolate ion from aryl N-(phenylsulfonyl)carbamates is positive (rho(-) = +2.93) while, for phenyl N-(substituted phenylsulfonyl)carbamates it is negative (rho = -0.66). An electrophilic intermediate, phenylsulfonyl isocyanate, was trapped with piperidine to give N-(piperidinocarbonyl)benzenesulfonamide. These results are consistent with an elimination-addition mechanism A(rh)D(H) + D-N (E1cB). In HCl solutions, solvent isotope effects k(obsd)(H2O)/k(obsd)(D2O) equal to 1.68 for 1a and 2.46 for Id have been measured. For molar concentrations of water lying between 40 and 55.5 M(-1), the rate of hydrolysis of la in 0.5 M HCl solutions increases in the presence of dioxan while it decreases with chloral. The Hammett rho values for the reactivity k,in acidic media of aryl N-(phenylsulfonyl)carbamates (rho = +0.87) and for phenyl N-(substituted phenylsulfonyl)carbamates (rho = +0.22) agree with the protonation of the oxygen atom of the leaving group. Trapping experiment for the hydrolysis of 1a and 1d in a chloroacetate buffer in the presence of 4-chloroaniline gave in both cases N-(((4-chlorophenyl)amino)carbonyl)sulfo. Reaction carried out in (H2O)-O-18 with O-16- containing substrate indicates that there is no exchange from water to the carbonyl group of the sulfonylcarbamate. These data support a general acid catalysis of the breakdown of the anion which cuts in depending on the leaving group ability.