Role of hydrophilic domains in determining the strength of hydrophobic interactions. A calorimetric study of the cross interactions in aqueous solutions of alkane-m,n-diols at 298.15 K

Abstract

Excess enthalpies of ternary aqueous solutions containing different alkane-m, n-diols have been determined at 298.15 K. The enthalpic interaction coefficients obtained were interpreted according to an interaction model which includes the presence of a preferential orientation between the two hydrated molecules, stabilized by the simultaneous juxtaposition of groups having the same effect on water structure. This model has been shown to be useful not only to explain the difference in the behaviour of positional, configurational and stereo isomers, but also to predict the value of the enthalpic interaction coefficient of polyhydroxylated substances in aqueous solution. There is evidence of a transition between the behaviour of alkane-m, n-diols and that of alkan-n-ols, related to the hindrance of juxtaposition of hydrophilic and hydrophobic domains. The difference in the alkyl chain length and/or the position of OH functional groups along the carbon skeleton contribute to this effect.