Vibrational Study of Thiodiglycolic Acid and Potassium Thiodiglycolate Salts

The Raman and infrared spectra of thiodiglycolic acid and its potassium salts in aqueous solution were recorded from 4000 to 200 cm−1. Vibrational assignments were made for all the observed wavenumbers on the basis of isotopic wavenumber shift, depolarization ratios and group wavenumber considerations and comparison with accepted assignments for certain vibrational modes in other similar compounds. The three compounds (the acid, the acid salt and the neutral salt) belong to theCssymmetry group, but their conformations are different. In the crystalline state, the acid salt has a strong hydrogen bond and appears to be of the A type according to Speakmann's classification.