Study on hydrogen bonding network in aqueous methanol solution by Raman spectroscopy.

Abstract

The Raman spectra of aqueous methanol solution with various concentrations were measured at room temperature and atmospheric pressure. We found that the CO stretching vibration mode of methanol showed a significant blue shift at Vm (Vm represents the volume fraction of methanol) >0.4, while the CH symmetric and asymmetric stretching vibration modes exhibited red shift under the same conditions. These results illustrate that the variation of hydrogen bond between methanol and water molecules lead to a phase transition of the methanol-water complex at Vm = 0.4. Furthermore, the red shift of the CH vibration mode indicates that there is no hydrogen bond formed between the CH3 group of methanol and water molecules. In addition, we found that the frequency shift of C-H is affected by the hydrogen bond C-O…H-O formed between methanol and water molecules, and the corresponding theoretical discussion is given. Finally, the phase transition process of methanol-water complex in methanol-water binary solution was given by theoretical analysis.