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.

Enthalpies of diln. of ternary aq. solns. contg. biuret or urea and alkane-n, m-diols were detd. by flow microcalorimetry at 298.15 K. The pairwise cross-interaction coeffs. of the virial expansion of the excess enthalpies were detd. The coeffs. are pos. and depend in a complex manner on the length of the alkyl chain of the hydroxylated substances. A balance between favorable hydrophilic-hydrophilic and repulsive hydrophilic-hydrophobic interactions is the factor that dets. the behavior of these systems. NMR relaxation time measurements were also performed: however, this technique does not show the complexity unravelled by calorimetry. For binary solns. of a,w-diols, a correlation is presented between the relaxation times and the enthalpic self-interaction coeffs.