Abstract
Infrared spectra were applied to the studies on the amido-imido tautomerism of the sulfonamide derivatives containing the heterocyclic rings such as thiadiazole and isoxazole. 2-Phenylsulfonamidothiophene was used as a model compound of the amidoform. From the pattern of the spectral change on N-deuteration and the comparison with the corresponding carboxylic acid amides in the region 1650∼1500 cm-1, it was found that 2-sulfonamidothiadiazoles exist in the imido-form, while 3-and 5-sulfonamidoisoxazoles exist in the amido-form in the solid state. For most of the sulfonamides the SO2 symmetric stretching frequencies of the imido-form were found to be lower than those of the amido-form.
