Basicity of nitrogen-sulphur(VI) compounds. part 2. Protonation equilibria of N-arylsulphamates using ultraviolet and nuclear magnetic resonance methods

The eouilibrium ArN(R)SO₃^–+ H⁺ ⇌ ArN[graphic omitted]RSO₃ – was examined using seven arylsulphamates and one mixed alkylarylsulphamate, i.e. N-methyl-N-phenylsulphamate. H₀ Values at half protonation, (H₀)_½, have been calculated, together with Bunnett and Olsen pK _BH⁺ values, from ionization data obtained from u.v. spectra. N.m.r. downfield shifts generally in deuteriosulphuric acid have been used for four of the compounds to obtain protonation data from which (H₀)_½ values have been calculated. The agreement between the (H₀)_½ values obtained by the two methods is generally good. Some recent Russian data agrees well with the Bunnett and Olsen pK _BH⁺ values. N-Protonation to give a zwitterion rather than O-protonation to give ArNHSO₃H is favoured.