Volume 59, Number 3, August 2002
|Page(s)||377 - 383|
|Section||Condensed matter: structure, mechanical and thermal properties|
|Published online||01 September 2002|
Water structure and solute association in dilute aqueous methanol
Department of Physics and Astronomy, The University
of Edinburgh Mayfield Road, EH9 3JZ, Edinburgh, UK
2 ISIS Facility, Rutherford Appleton Laboratory Chilton, Didcot, Oxon, OX11 OQX, UK
3 Department of Physics and Astronomy, University College London Gower Street, WC1E 6BE, London, UK
Accepted: 2 May 2002
The molecular structure of a dilute aqueous methanol solution (1:19 molar ratio) is studied using neutron diffraction with hydrogen/deuterium isotope substitution. The Empirical Potential Structure Refinement (EPSR) method is used to create a structural model of the solution which is consistent with the measured diffraction data. Direct evidence of methanol association is found with more than 80% of the methanol molecules in clusters of 3 to 8 molecules. Contrary to several previous studies, and conventional views on the hydrophobic interaction, no enhancement of the water structure surrounding the non-polar groups is observed. Consistent with results from other related systems, a compression of the second-neighbour water-water contact distance is observed that may be a structural feature of the hydrophobic driving force.
PACS: 61.12.-q – Neutron diffraction and scattering / 61.20.Qg – Structure of associated liquids: electrolytes, molten salts, etc / 82.70.Uv – Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems (hydrophilic and hydrophobic interactions)
© EDP Sciences, 2002
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