Predicting the Relative Solubilities of Racemic and Enantiopure Crystals by Density-Functional Theory

Isolation of chiral molecules as pure enantiomers remains a fundamental challenge in chemical research. Enantioselective enrichment through preferential crystallization is an efficient method to achieve enantiopure compounds, but its applicability depends on the relative stability of the enantiopure and racemic crystal forms. Using a simple thermodynamic model and first-principles density-functional calculations, it is possible to predict the difference in solubility between the enantiopure and racemic solid phases. This approach uses dispersion-corrected density functionals and is capable of accurately predicting the solution-phase entantiomeric excess to within about 10% of experimental measurements on average. The accuracy of the exchange-hole dipole moment (XDM) model of dispersion enables the viability of the proposed method.