Abstract
The development of accurate models to predict the solvation, solubility, and partitioning of nonpolar and amphiphilic compounds in aqueous environments remains an important challenge. We develop state-of-the-art group-interaction models that deliver an accurate description of the thermodynamic properties of alkanes and alcohols in aqueous solution. The group-contribution formulation of the statistical associating fluid theory based on potentials with a variable Mie form (SAFT-γ Mie) is shown to provide accurate predictions of the phase equilibria, including liquid–liquid equilibria, solubility, free energies of solvation, and other infinite-dilution properties. The transferability of the model is further exemplified with predictions of octanol–water partitioning and solubility for a range of organic and pharmaceutically relevant compounds. Our SAFT-γ Mie platform is reliable for the prediction of challenging properties such as mutual solubilities of water and organic compounds which can span over 10 orders of magnitude, while remaining generic in its applicability to a wide range of compounds and thermodynamic conditions. Our work sheds light on contradictory findings related to alkane–water solubility data and the suitability of models that do not account explicitly for polarity.
Highlights
The complex intermolecular solvation interactions between nonpolar moieties and water and, in particular, the hydrophobic effect[1−3] play a central role in determining the structure and properties of biomolecules, their compartmentalization, and subsequent organization in the living cell.[4]
We develop novel models for the accurate prediction of vapor−liquid, liquid−liquid, and vapor− liquid−liquid equilibria (VLLE) of aqueous solutions of alkanes and alcohols within the statistical associating fluid theory (SAFT)-γ Mie group contribution
Most solutes behave in a more nonideal manner in the water-rich phase[6,129], and we find that an accurate prediction of γi,WR plays a vital role in the reliability of the description of Ki,OW
Summary
The complex intermolecular solvation interactions between nonpolar moieties and water and, in particular, the hydrophobic effect[1−3] play a central role in determining the structure and properties of biomolecules, their compartmentalization, and subsequent organization in the living cell.[4]. The Gibbs free energy of hydration can be obtained from experimental aqueous solubility data (or from Henry’s law constants or activity coefficients of a solute in aqueous solution at infinite dilution).[83] The larger uncertainties reported in the experimental of n-alkanes and n-alkan-1-ols in water predicted with the SAFT-γ Mie approach are in good agreement with the experimental data.[102,126] Some deterioration in the agreement is seen for the longer n-alkanes (carbon number >11103), though we note there are discrepancies among the different sets of experimental data[103] and simulation results.[12] As in the case of ΔGis,oj l, the γi∞,j data for long n-alkanes are commonly obtained from aqueous solubility data[102,103] (cf Figure 6), which can be extremely difficult to measure. Further details of this effective approach and its impact on the thermodynamic properties of the system is the subject of future work
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