We request beam-time for high-resolution neutron diffraction in conjunction with hydrogen/deuterium isotopic labelling and EPSR analysis to probe the detailed 3-dimensional spatial and orientational structure of methanol-olefin (1-pentene and 1-hexene) mixtures above the Upper Critical Solution Temperature (UCST). In addition to providing decisive information regarding the nature of the proposed -OH¿¿¿π hydrogen bonding structure, the use of NIMROD will also allow us to investigate the nature of mixing/demixing of solvent and solute above the UCST. For each olefin 2 compositions will be studied at 25 and 75 mol % solute with isotopic labelling of protons on both solvent (methyl and hydroxyl groups) and solute. For each sample we propose 8 isotopic compositions in total.