Basicity of nitrogen–sulphur(VI) compounds. Part 3. Protonation equilibria of sulphamates using potentiometric and 13C nuclear magnetic resonance methods

Abstract

Potentiometric and ¹³C n.m.r methods have been used to study the sulphamata equilibria in Scheme 1. pK_a values for step b have been determined for 19 sulphamates including seven hetero-sulphamates which contain an additionaI nitrogen atom. The determination of pK₁(for the hetero-nitrogen atom) and pK₂(for the sulphamate nitrogen atom) required the use of a computer program in a few instances where the basicities of the two nitrogens were close (overlapping pK_a values)- pK_a values (ca. 12) for step a have been determined for five compounds. Step c has been studied in H₂SO₄ and the p_Kvalues (–1.2 to –1.74 from the Bunnett and Olsen equation) have been determined for three compounds