DIELECTRIC BEHAVIOR STUDY OF XYLITOL ASSO CIATED TO WATER-MOLECULES

The permitivities, refractive indices and specific volumes of very dil ute aqueous solutions of xylitol were measured at 25%C. The experiment al dipole moment calculated using Buckingham's equation, was found to be a <(mu)over bar(Exp)> = 8.46 D which is very far from 4.51 D, the v alue obtained vectorially. In order to calculate the dipole moment of xylitol in an aqueous medium, it was necessary to know its most probab le conformation. Then, taking into account as many associations as pos sible between the solute molecule and a finite number of water dipoles , as was allowed by molecular parameters, a M(mu)over bar>(Theor)> = 8 .49 D was obtained for the associated entity. Comparing these experime ntal and theoretical values, the conclusion was that an average of the hydrogen bonded water dipoles could be surrounding the solute molecul e. The validity of the postulated solute - solvent association is supp orted by the fact that the experimental partial molar volume of the so lute is different from the calculated one.