SOLUTE WATER INTERACTIONS IN THE ORGANIC-PHASE OF A BIPHASIC SYSTEM .1. STRUCTURAL INFLUENCE OF ORGANIC SOLUTES ON THE WATER-DRAGGING EFFECT

The ''water-dragging'' effect is characterized by the amount of water ''dragged'' into a water-insoluble organic solvent by a solute partiti oning between water and this solvent.1 In this study, 62 structurally diverse compounds (ortho-, meta-, and para-substituted phenols, carbox ylic acids, alcohols, amines, miscellaneous aprotic solutes, and diast ereomeric ephedrines) were investigated. The results were analyzed by an equilibrium model and ''pressed in terms of the macroscopic stoichi ometry of hydrates and an equilibrium constant of hydrate formation. T he macroscopic stoichiometry of hydrates being close to one (range 0.5 -1.5), a normalized equilibrium constant (log K(w)') was calculated fo r a stoichiometry fixed to a value of one. On this basis, the water-dr agging effect was shown to be due primarily to the H-bond-donor acidit y of solutes and secondarily to their H-bond-acceptor basicity. In add ition, intramolecular effects (e.g., internal H-bonds) and solvent acc essibility strongly modulate the water-dragging effect.