Solute--water interactions: do polyhydroxy compounds after the properties of water?

The interactions between PHCs and water, like those between water molecules, are governed by hydrogen bonding. The details of these interactions are very sensitive to spacings and orientations of the -OH groups on the solute molecules. Where different conformers can coexist in solution, the aqueous solvent acts so as to favor the conformer with the largest number of equatorial -OH groups, because of their spatial compatibility with water. Because of this compatibility, aqueous solutions of PHCs have the tendency to supersaturation and incomplete freezing, manifestations of the phenomenon known as bound water which is, however, a misnomer. The range of water structure perturbation is probably governed by hydration forces which appear to dominate at solute-solute distances of less than 3 nm and which decay exponentially. Although on a single hydrogen bond basis the hydration effects are marginal, they nevertheless are responsible for many macroscopic phenomena, e.g., gel formation, liquid crystals, and protection against dehydration.