Role of solutes in the hydrogen bonding of water-ethanol mixtures

Abstract

The properties of the hydrogen bonding of water-ethanol in alcoholic beverages have not been sufficiently clarified. We investigated possible factors that could affect the hydrogen-bonding structure of water-ethanol on the basis of proton nuclear magnetic resonance (1H NMR) chemical shifts of the OH of water-ethanol and Raman OH stretching spectra. Not only acids (H + and HA : un-dissociated acids) but also bases (OH- and A-: conjugate-base anions from the weak acids) caused a development in the hydrogen-bonding structure of water-ethanol media. We also demonstrated that the hydrogen bonding was strengthened by chemical components in alcoholic beverages (whiskey, Japanese sake, and shochu). This suggested that hydrogen-bonding donors as well as acceptors in alcohol beverages, which exist as initial components or are gained later on, should cause a promoted proton-exchange between water and ethanol molecules. © 2008 The Japan Society for Analytical Chemistry.