Solubility of nonelectrolytes in polar solvents. V. Estimation of the solubility of aliphatic monofunctional compounds in water using a molecular surface area approach

The molecular surface areas for 158 aliphatic hydrocarbons, olefins, alcohols, ethers, ketones, aldehydes, esters, and fatty acids have been computed and correlated with their aqueous solubilities. The hydrocarbon and functional group contributions to the free energy of solution are compared and discussed with particular regard to the chosen standard state. The results indicate that the functional group contributions to the free energy of solution in water are nearly equivalent from the pure liquid standard state while being significantly different when the gas phase (1 mmHg) standard state is chosen. The interpretation of the differing hydrocarbon surface area slopes is shown to be complicated by mutual miscibility considerations (water solubility in the pure liquid) and by the presence of curvature for the longer chain length (greater than C₁₀) compounds. The curvature in the alcohol and fatty acid data is shown to become very evident when correction is made to the pure (supercooled) liquid standard state for the solid compounds. Finally the surface area method is shown to hold considerable promise in its extension to the solubility estimation of complex organic molecules with limited aqueous solubilities.