POLAR-SOLVENTS EFFECT ON THE DIPOLAR MOMENT OF CATECHOL

In order to study the behavior of catechol in polar solvents the experimental changes of permitivities, refractive indices and specific volumes of very dilute aqueous and ethanolic solutions at 25-degrees-C were analyzed. With these values and using Buchingham's eq. the experimental dipole moments were determined in both solvents and they resulted: mu(cat)BAR = 11,45 D in water and mu(cat)BAR = 7,71 D in absolute ethanol. By comparying this mu-BAR values with those vectorially calculated assuming that one catechol molecule is attached to several solvent molecules, and that this set is immersed in a solvent continuum, a good approximation is found. For this reason, we can deduce that the postulated models for intermolecular association like hidrogen bonding are acceptable. These association is confirmed by the experimental results corresponding to the solute partial molar volume.