Physico-chemical behaviour of sulpha drugs. Spectroscopic trends and conjugation in phenylsulphonylguanidine derivatives

Abstract

The stretching frequencies of the sulphonyl group and the u.v. spectra of phenylsulphonylguanidine, and its ortho-, meta-, para-amino, -methyl, -chloro, and -nitro-derivatives have been measured. For p-aminophenyl-sulphonamidoguanidine which, as well as the ring N-methyl derivatives of p-aminophenylsulphonamido-pyridine (SP) and -thiazole (ST), shows electronic properties intermediate between those of the neutral[N(1)-methyl derivatives of SP and ST] and of the anionic species (sodium salts of SP and ST), the occurrence of the imide or zwitterion structure was confirmed. The i.r. results indicate that no effective conjugation occurs between the aryl and the S–O bonds, while the u.v. spectra give evidence of the interaction between the two chromophores bonded to the SO₂ group. The experimental data seem to support a previously postulated model for conjugation where (a) the conjugation between the two chromophores can occur via an empty d orbital of the expanded valence shell of the sulphur atom not entering the SO₂π-system, and (b) a further interaction operates between the SO₂π-system and the guanyl portion of the molecule.