The molecular structure of alcohol-water mixtures determined by soft-X-ray absorption and emission spectroscopy

We have examined the influence of the intermolecular interaction on the local electronic structure by using X-ray absorption and emission spectra of liquid methanol, water, and their mixtures (in molar ratios of 9:1 and 7:3). We find a strong involvement of hydrogen bonding in the mixing of water and methanol molecules. The local electronic structure of water and methanol clusters, where water cluster is bridging within a 6-member open-ring structured methanol cluster, is separately determined. The experimental findings suggest an incomplete mixing of water-alcohol systems and a strong self- association between methanol chain and water cluster through hydrogen bonding. The enhancement of joint water-methanol open-ring structure owes the explanation to the loss of entropy of the aqueous solutions. (C) 2004 Elsevier B.V. All rights reserved.