Basicity of nitrogen–sulphur(VI) compounds. Part 4. Ionization of di- and tri-substituted sulphamides

Abstract

Potentiometric and u.v. methods have been used to study the ionization equilibria of di- and tri-substituted sulphamides: RNHSO₂NHR [graphic omitted] R[graphic omitted]SO₂NHR [graphic omitted] R[graphic omitted]SO₂[graphic omitted]R RNSHO₂NME₂ [graphic omitted] R[graphic omitted]SO₂NMe₂ pK_a Values for equilibrium a have been determined for nine di- and five tri-substituted sulphamides, sulphamide, and phenylsulphamide in 60% v/v ethanol–water. Ionization data for equilibrium b have been measured for seven diarylsulphamides in aqueous potassium hydroxide. Since neither H_– nor H_2– acidity functions are suitable for describing the ionizations occurring a number of other methods, e.g. the modified Marziano–Cimino–Passerini method, have been used to obtain thermodynamic pK_a values. The agreement between the pK_a values obtained by the various methods is good. The effect of substituents on both equilibria (a and b) is similar.