Aggregation of molecules in liquid methyl alcohol and its solutions: Raman spectra and ab initio calculations

Spectral composition of Raman bands of CO (CH3OH) and OD (CH3OD) vibrations are different in different polarized components of the scattered light. The difference is related to complexity of the bands: presence within the band of several lines with different magnitudes of depolarization ratio, which correspond to different aggregated formations of methyl alcohol. Quantum-chemical calculations in B3LYP 6-31++G(d,p) approximation and in RHF 6-31++G(d,p) approximation for isolated monomer molecules, dimers and trimers showed that there is an intramolecular H-bond between one of H atoms of CH3 group and O atom of the same molecule. Calculations showed that for CH3OH trimer the most profitable aggregation is a closed ring with the energy profit of 57.4 kJ/mol. Significant half-width of OD band is conditioned partially by overlapping of the bands of different aggregated formations.