Solution properties of ethanol in water

The packing propensity of ethanol in aqueous solution is very unusual, yet ethanol finds extensive use both in the food and the pharmaceutical industr y. An analysis of the solution properties of increasing concentrations of e thanol in water at 20 degrees and 37 degrees C reveals valuable information about its packing characteristics. Apparent molar and specific volumes pro vide information about the interaction of ethanol with surrounding water st ructure. Isentropic apparent molar and specific compressibilities indicate the extent to which the hydration layer around the ethanol molecules can be compressed. Compressibility hydration numbers show the number of water mol ecules that are displaced by the introduction of the ethanol to:water. The enhanced packing efficiency of ethanol in water at low concentrations, is a ffected by the formation of cage-like structures around the hydrophobic end of the molecule. At high concentrations, however, linear chains or rings o f ethanol molecules are formed which change its mode of packing within the three-dimensional structure of water. These effects may be used to help exp lain the mechanism of action of ethanol in food, pharmaceutical and other a pplications. (C) 1999 Published by Elsevier Science Ltd. All rights reserve d.