Role of hydrophilic interactions in sustaining preferential orientations: calorimetric and nuclear magnetic resonance studies of ternary aqueous systems containing a destructuring agent and hydroxylated compounds at 298.15 K

Abstract

Enthalpies of dilution of ternary aqueous solutions containing biuret or urea and alkane-n, m-diols have been determined by flow microcalorimetry at 298.15 K. The pairwise cross-interaction coefficients of the virial expansion of the excess enthalpies were determined. The coefficients are positive and depend in a complex manner on the length of the alkyl chain of the hydroxylated substances. A balance between favourable hydrophilic–hydrophilic and repulsive hydrophilic–hydrophobic interactions is the factor that determines the behaviour of these systems. NMR relaxation time measurements have also been performed: however, this technique does not show the complexity unravelled by calorimetry. For binary solutions of α,ω-diols, a correlation is presented between the relaxation times and the enthalpic self-interaction coefficients.