Modeling and experimental evaluation of enantioselective liquid-liquid extraction of (D, L)-4-chlorophenylglycine in a biphasic system

• 4-Chlorophenylglycine enantiomers extracted through an interfacial reaction process.
• The model predicts extraction performance as a function of key operating parameters.
• The extraction model predictions are in good agreement with the experiment.
• Optimal conditions are pH 7 and 1 mmol/L (S)-BINAP by experiment and simulation.

Enantioselective Liquid-Liquid Extraction (ELLE) is a potentially attractive technology for the production of enantiopure compounds. The purpose of this research is to investigate ELLE of 4-chlorophenylglycine (CPG) enantiomers with metal-BINAP complexes as enantioselective extractants. The metal complexes were synthesized by the complexation of (S)-2,2’-bis(diphenylphosphino)-1,1’- binaphthalene (BINAP) with different central ions, among which, palladium complex allowed the separation of the CPG enantiomers with the highest operational selectivity. Efficiency of the extraction depends, often strongly, on a number of process variables, including types of organic solvents, pH of the aqueous phase, concentration of host and substrate, and temperature. In order to better understand the extraction process, equilibrium of the system was modeled by an interfacial reaction model. Important parameters required by the modeling, such as complexation equilibrium constant, were determined experimentally. When coupled with the parameters, extraction performance can be predicted by the model. By modeling and experiment, an optimal extraction condition concerning pH of 7 and the host concentration of 1·10−3 mol/L was obtained with high enantioselective (α) of 1.862 and performance factor (pf) of 0.056.