Prediction of the aqueous solubility of proton-acceptor oxygen-containing compounds by the mobile order solubility model

The general solubility equation for real solutions derived from mobile order theory is successfully applied to predict the aqueous solubility of 232 oxygen-containing proton acceptor substances, i.e., ketones, ethers, esters and aldehydes. Obtained from a strictly thermodynamic basis, the model leads to a better understanding of the solution process and of the factors that determine solubility in aqueous solution. The analysis of the relative importance of the various terms contributing to the overall solubility demonstrates that the solubility in water is essentially governed by the hydrophobic effect. This effect is also responsible for the lowering of solubility with increasing molar volume of the solute. A positive effect on solubility is brought about by H-bond formation between water and solute molecules. The mobile order thermodynamics provides explanations for the empirically observed solubility-volume linear relationships.