Kinetics and mechanism of the acid-catalysed hydrolysis of sodium N-1-naphthylsulphamate

The kinetics of the acid-catalysed hydrolysis of sodium N-1-naphthylsulphamate have been measured in hydrochloric, perchloric, and sulphuric acids over a wide range of acid strengths. Rate maxima are observed for hydrolysis in each acid. On the basis of Bunnett ω* plots, the solvent isotope effect, and salt effects, the mechanism is seen as involving a pre-equilibrium protonation followed by a rate-determining A-2 type nucleophilic attack by water at sulphur. Entropy data, however, suggest that in the rate-determining step considerable nitrogen-sulphur bond rupture may occur prior to bond formation with the nucleophile. The pK_BH+ value for N-1-naphthylsulphamate is -1.45 (based on the H₀ scale).