Temperature dependence of structural quantum effects in liquid methanol

¹ Department of Physics, University of Guelph - Guelph, Ontario, Canada N1G 2W1
² IPNS Division, Argonne National Laboratory 9700 S. Cass Ave., Argonne, IL 60439, USA
³ ISIS Facility, CLRC Rutherford Appleton Laboratory Chilton, Oxon OX11 OXQ, UK
⁴ Hamburger Synchrotronstrahlungslaboratorium HASYLAB at Deutsches Elektronen Synchrtron DESY - Notkestr. 85, 22603 Hamburg, Germany
⁵ European Synchrotron Radiation Facility BP 220, F-38043 Grenoble Cedex, France

Received: 4 January 2001
Accepted: 28 May 2001

Abstract

High-energy electromagnetic radiation scattering techniques have been used to measure the structural differences between liquids composed of four different isotopes of methanol ( and ) at temperatures of and . We measured the magnitude of the isotopic effect, which increases with decreasing temperature and comprises of both intramolecular and intermolecular effects. Intramolecularly, the C-O, O-H, and to a lesser extent the C-H bond lengths, shorten upon deuteration. Intermolecularly, the winding hydrogen bonded chain structure is affected significantly. The results show that hydrogenated simple alcohols are more disordered liquids than deuterated alcohols at the same temperature. Substitution at the methyl site is compared to substitution at the hydroxyl site and the effect is shown to increase more rapidly as temperature is decreased.