Local structures of aqueous methanol (MeOH) solutions were studied by O and C K-edge XAS, where the hydrogen bond (HB) structures between MeOH and water molecules were obtained at the O K-edge, and the local structures around the methyl group of MeOH molecules were obtained at the C K-edge. The C K-edge XAS spectra of (MeOH)x(H2O)1−x show three concentration regions, whose molecular structures were discussed with the help of the molecular dynamics simulations. In the region I (1.0 > x > 0.7), a small amount of water molecules exists separately around HB networks of MeOH clusters. In the region II (0.7 > x > 0.3), the hydrophobic interaction of the methyl group is dominant due to the increase of mixed MeOH‒H2O clusters. In the region III (0.3 > x > 0.05), MeOH molecules are separately embedded in HB networks of water.
