Huyskens, PL; Haulait-Pirson, MC; Hanssens, I; Mullens, J
Measurements were made at 298.2 K of the solubility of water in cyclohexane, carbon tetrachloride, and benzene in the presence of some ten aliphatic alcohols, the concentration, FB, of which varied from 0.25 to 4 mol dm-3. The solubility of water, FW, increases in a nonlinear way on increasing FB. The function is nearly similar for all the alcohols provided the activity of water in the aqueous phase in equilibrium remains approximately unity. For these alcohols a model of water absorption is proposed which fits with the experimental FW/FB function. This model is consistent with the fact that the solubility of water in the various alcohol solutions is not related to the association of the alcohol in the organic phase. According to this model, water is incorporated in the association chains of the alcohol, the complexes formed by water and the alcohol participating in the association processes just in the same way as the monomolecules of alcohol. This incorporation takes place by addition of water at the head or at the tail of the chains or by insertion in the chain or by lateral fixation on an oxygen atom of the chain. However, the "mono-incorporated" water molecules may become involved in a second chain at the intervention of their second O-H group or their second lone pair of electrons, or both of them, realizing thus an interconnection of two alcohol chains. A third possibility which becomes more and more important on increasing Fw is the formation of hydrogen bonds between water molecules already incorporated in an alcohol chain, thus realizing an association chain of mono-incorporated water molecules. The equilibrium constants Kinc* for the first incorporation are of the order of 11.7, 4.6, and 1.7 dm3 mol-1, respectively, in cyclohexane, carbon tetrachloride, and benzene. The equilibrium constants Kinc** for the second incorporation in alcohol chains are respectively of the order of 2.5, 2.3, and 2 dm3 mol-1 whereas the addition constants of mono-incorporated water molecules KWW** are of the order of 6.1, 5.6, and 4.4 dm3 mol-1 in the three solvents. For FB ≥ 1 mol dm-3, the majority of the water molecules have two O-H groups or two lone pairs of electrons or both involved in H bonds with the surroundings. The implication of the second O-H group in H bonds makes water as a solute more basic than the alcohols. The higher proton captor power of water compared with methanol in t-BuOH solution was recently demonstrated by Chantooni and Kolthoff. 1980 American Chemical Society.