Hydration of methanol in aqueous solutions: a Raman spectroscopic study

High-resolution Raman spectroscopy was used to study methanol-water mixture s over the whole concentration range. We report a highly non-linear depende nce of the carbon-oxygen and carbon-hydrogen stretching frequencies with co mposition. The difference between the polarized and depolarized frequencies of the carbon-oxygen stretching mode (non-coincidence effect) was also mea sured. Taken together, the data suggest a global picture of the progressive hydration of methanol: water first breaks up the molecular chains which ex ist in pure methanol, and then completely hydrates the hydroxyl groups befo re solvating the hydrophobic methyl groups.