Interactions between cations and sugars. Part 4.—Free energy of interaction of the calcium ion with some aldopentoses and aldohexoses in water at 298.15 K
Abstract
The free energies of interaction of ribose, arabinose, lyxose, xylose, glucose, mannose, galactose, talose and allose with CaCl2 and KCl have been determined in water at 298.15 K. The electrochemical method used for these determinations leads to reaction properties, in particular to the association constants, in sufficiently dilute solutions for these properties to be thermodynamically meaningful, unlike n.m.r. methods, which require solutions concentrated both in sugar and in salt. It appears that the constants presented here are distinctly smaller than those determined from n.m.r. data. This work also shows that, depending on the structure of the sugar and on its hydration, the interactions between the sugar and Ca2+ can be either attractive (association) or repulsive (salting-out).