THE HYDROPHOBIC PROPENSITY OF WATER TOWARD AMPHIPROTIC SOLUTES - PREDICTION AND MOLECULAR-ORIGIN OF THE AQUEOUS SOLUBILITY OF ALIPHATIC-ALCOHOLS

A quantitative expression of the hydrophobic effect for amphiphilic so lutes in water is developed in the frame of the nonergodic thermodynam ics of mobile order in hydrogen-bonded liquids. In the case of aliphat ic alcohols, the new expression leads to reduction of the hydrophobic propensity of water with respect to that exerted towards substances wi th no hydrogen bonding capacity. The reduction originates from the pos sible insertion of the alcohol molecules in the weakest hydrogen bond chain of water; hence, strengthening the hydrogen bonding network of w ater. Combined with the previous solubility model derived from mobile order thermodynamics, the new expression allows correct predictions of the solubility of 86 liquid and solid branched- and straight-chain al cohols in water at 25 degrees C, and provides better understanding of their behavior in aqueous solution. The model is furthermore applied t o the estimation of the aqueous solubility of 12 monohydroxysteroids.