Chemical shift study of liquid and supercritical methanol

Chemical shifts of the OH proton in methanol referred to the CH3 proton have been measured in the temperature range from 289 to 580K. The reduced densities rho(r) of the sample are 0.183, 0.256, 0.372, 0.622 and 1.008 in the supercritical condition. The chemical shifts of the non-hydrogen-bonded proton have been determined as delta(N-HB) = -3.45 +/- 0.10 ppm from the density dependence in the supercritical region. The thermodynamic model which takes account of methanol cluster distribution provides the degree of hydrogen bonding. The number of hydrogen-bonded clusters decreases with increasing temperature and decreasing density. In the supercritical region, the results of the chemical shift are consistent with the thermodynamic model. (C) 1998 Elsevier Science B.V. All rights reserved.