Temperature dependence of associative equilibria of DMSO according to raman scattering spectra

Raman scattering spectra of dimethyl sulfoxide (DMSO) are studied in the area of the line corresponding to symmetric CSC stretching vibrations of the molecule. It is established that this line is composed of a low-frequency component that corresponds to the vibrations of monomeric molecules and a high-frequency component that corresponds to the vibrations of DMSO dimers. Values of self-association equilibrium constants K _a varying in range from 0.20 (23°C) to 0.081 (100°C) are obtained. Since the intensities of the respective components of the line contour are proportional to the compound’s concentrations, the enthalpy of DMSO self-association (ΔH = ?11.7 ± 0.9 kJ/mol) is determined from the temperature dependences.