Interactions entre les cations et les sucres. I. Évaluation de l'enthalpie libre d'interaction Ca2+ − D-(−)-ribose dans l'eau à 25 °C

The interaction of the two isomeric pentoses D-(−)-ribose and D-(−)-arabinose with the Ca2+ ion in aqueous solution is studied with the help of two types of electrochemical cells (with and without liquid junction) including a liquid-membrane Ca2+-selective electrode. Some of the D-(−)-ribose isomers contain a sequence of hydroxyl groups which can interact specifically with the cation. The measurement of the Gibbs free energy of transfer of Ca2+ between water and the sugar solutions allows one to calculate a characteristic pair-interaction parameter. This specific interaction can also be characterized by its association constant: β1 = 0.93. The two approaches are studied and their coherence is shown.