Enantioselective liquid-liquid extraction of DL-mandelic acid using chiral diphosphine ligands as extractants.

In order to expand the application range of chiral diphosphine ligands, (S)-BINAP, (S)-SEGPHOS, and (S)-MeO-BIPHEP were employed as extractants to recognize DL-mandelic acid. The results indicated that (S)-SEGPHOS-Cu exhibited considerable ability to recognize DL-mandelic acid with operational enantioselectivity (α) of 2.677. The process of extraction of DL-mandelic acid using (S)-SEGPHOS-Cu as extractant was systematically investigated. Performance factor (pf) was adopted to comprehensively evaluate the extraction. After optimization by response surface methodology (RSM), the optimal extraction condition is temperature of 5.5°C, (S)-SEGPHOS-Cu concentration of 3.0 mmol/L, and pH of 8.0. And the predicted and experimental maximum values of pf were 0.26374 and 0.26839, respectively.