Solid-liquid equilibria of mandelic acid enantiomers in two chiral solvents: experimental determination and model correlation

Abstract

A study of the ternary solubility phase diagrams of enantiomeric mandelic acid species in the chiral solvents (S)-ethyl lactate and (2R,3R)-diethyl tartrate has been carried out. The solubility measurements were conducted for enantiomeric compositions between the racemic compound and the single enantiomer for temperatures between (273 and 333) K. Experimental results showed no evidence of differences in the solubility of both enantiomers in both chiral solvents. The ideal solubility curves of the mandelic acid species as well as of the racemic compound revealed large deviations from experimental data. The nonrandom two-liquid (NRTL) model was applied to quantify and parameterize the solid-liquid equilibria (SLE) by means of activity coefficients. Hereby, pronounced solute-solute interactions were found, while solvent-solute interactions were interpreted as being nonchiral specific