Hydrophobic interactions in the aqueous solutions of alkan-1,2-diols. Calorimetric and spectroscopic studies at 298.15 K

Enthalpies of dilution in water are determined for ternary aqueous solutions containing two of the following alkan-1,2-diols: ethane-1,2-diol, propane-1,2-diol, butane-1,2-diol, pentane-1,2-diol and hexane-1,2-diol. The derived enthalpic interaction coefficients are interpreted in terms of the interaction of two hydrated molecules through a preferential orientation, ‘side on’, stabilized by the preferred interaction between the hydroxyl groups. Other effects are considered, which lead to a unifying rationalization, common to alkanols and other isomeric diols.Further evidence for a ‘side on’ orientation is given by nuclear relaxation time studies on the binary and ternary aqueous solutions of propane-1,2-diol and hexane-1,2-diol.