Equilibrium Studies on Enantioselective Liquid-Liquid Extraction of Phenylalanine Enantiomers Using BINAP-Metal Complexes

The deparation of phenylalanine (Phe) enantiomers by reactive liquid-liquid extraction with (s)-BINAP-metal complexes as enantioselective extractants was investigated. Metal complexes formed by different central ions with (s)-BINAP as a ligand were used as chiral extractants, among which the CuPF6-(s)-BINAP complex (BINAP-Cu) allowed the separation of the Phe enantiomers with the highest operational selectivity. The efficiency of the extraction depends, often strongly, on a number of process variables, including the types of metal precursors and organic solvents, pH of the aqueous phase, concentration of extractant and substrate, and temperature. To better understand the extraction process, an interfacial reaction model was established. The best conditions involving a pH value of 7, feed concentration of 2.0.10(-3) mol.kg(-1), BINAP-Cu concentration of 1.59.10(-3) mol.kg(-1), and temperature of 5 degrees C are obtained by modeling and optimization with a high enantioselectivity of 5.2038. The model quantitatively predicts the extraction performance and provides a simple computational approach to process optimization.