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 fo r 5-amino-1,3,4-thiadiazole-2-sulfonamide. The molecular geometry was optim ized by means of the DFT methods of quantum chemistry (B3LYP/6-31G**), resu lting in a structure which agrees quite well with that obtained by X-ray di ffraction. The wavenumbers corresponding to the normal modes of vibration w ere calculated using the same approximation and the associated force field converted to a set of local symmetry coordinates, with subsequent calculati on of the potential energy distribution. An assignment of the observed band s is proposed on the basis of such calculations and the comparison With rel ated molecules. (C) 2001 Elsevier Science B.V. All rights reserved.