Sulphonamides. II. Structure and Tautomerism of Sulphapyridine, Sulphathiazole, and Sulphanilylbenzamidine

Abstract

By the study of ultraviolet absorption spectra and comparison with methyl derivatives of known structure it is shown that the two forms of arylsulphonylbenzamidines described by Barber (1943) are tautomers, the more stable one having structure I. In dilute solution, sulphathiazole is found to be mainly X, and sulphapyridine a mixture of XIII and XIV in a ratio which depends on the solvent and can be influenced by changes on the p-amino group. Bands of the spectra are assigned to structural features of these molecules.