Raman spectroscopic studies on hydrogen bonding in methanol and methanol/water mixtures under high temperature and pressure

The Raman spectral shifts of methanol in pure methanol and methanol/water m ixtures have been measured from room temperature up to 600 K under pressure s of 10 or 20 MPa. In pure methanol, the gradual spectral changes of indivi dual vibrational modes against the temperature indicate weakening of the in termethanol hydrogen bonding with temperature, but imply that it still rema ins at the critical temperature of methanol. In the methanol/water mixtures with low methanol contents, the Raman peaks of methanol do not move apprec iably at temperatures lower than 600 K, which indicates that the methanol m olecule is isolated in a water cage and the structure remains as it is up t o 600 K. (C) 1999 Elsevier Science B.V. All rights reserved.