AQUEOUS SOLUBILITY PREDICTION OF ENVIRONMENTALLY IMPORTANT CHEMICALS FROM THE MOBILE ORDER THERMODYNAMICS

Applied to the aqueous solubility of only-sligthly polar compounds wit h no hydrogen bond donor capacity, the quantitative development of the thermodynamics of mobile order results in a very simple nearly linear predictive solubility equation requiring only the molar volume of the solute and its melting properties in the case of solids. Enhancement of the solubility by weak solvation effects associated to the proton-a cceptor ability of the solute towards water is taken into account thro ugh standard stability constants reflecting the functionality, the deg ree of unsaturation and cyclization of the molecule. Accordingly, the molar aqueous solubility of a diverse set of 531 chemicals of environm ental relevance is predicted with an average absolute error of 0.37 lo g units though the solubilities span over more than 12 orders of magni tude. The analysis of the relative importance of the terms contributin g to the solubility demonstrates that the poor solubility of low-polar ity compounds in water is merely the result of the hydrophobic effect and of its extremely rapid increase with the size of the solute. The m obile order thermodynamics also provides explanations for the empirica lly deduced solubility-volume linear relationships. (C) 1997 Elsevier Science Ltd.