Infrared and Raman spectra of 5-amino-1,3,4-thiadiazole-2-sulfonamide (Hats). Experimental data and quantum chemistry calculations

The infrared and Raman spectra in the range 4000–50 cm-1 were obtained for 5-amino-1,3,4-thiadiazole-2-sulfonamide. The molecular geometry was optimized by means of the DFT methods of quantum chemistry (B3LYP/6-31G**), resulting in a structure which agrees quite well with that obtained by X-ray diffraction. The wavenumbers corresponding to the normal modes of vibration were calculated using the same approximation and the associated force field converted to a set of local symmetry coordinates, with subsequent calculation of the potential energy distribution. An assignment of the observed bands is proposed on the basis of such calculations and the comparison with related molecules.