ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7
Equilibrium of chiral extraction of 4-nitro-d,l-phenylalanine with BINAP metal complexes
Jia-Jia Liu, Guo-Hui Wu, Ke-Wen Tang, Xiong Liu, and Pan-Liang Zhang
College of Chemistry and Chemical Engineering, Central South University, Changsha, 410083, Hunan, China
Abstract: The enantioselective extraction of 4-nitro-phenylalanine (Nphy) was studied with metal-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) complexes as the chiral selector. The complex with palladium (BINAP-Pd) exhibits the highest selectivity out of the selectors studied, which is solubilised in the organic phase and preferentially extracts d-Nphy from the aqueous phase. Efficiency of extraction depends, often substantially, on a number of process variables, including types of organic solvents and metal precursors, concentration of ligand, pH, and temperature. A reactive extraction model was established to interpret the experimental data. The equilibrium formation constants and other important parameters required by the model were determined experimentally. The equilibrium formation constants were 6.73 and 1.93 for d-Nphy and l-Nphy. By way of modelling and experiment, an optimal extraction condition with pH of 7 and BINAP-Pd concentration of 1 mmol L−1 was obtained with enantioselectivity (α) of 3.37, which was close to the maximum of 3.48, and a performance factor (pf) of 0.195. The model was verified experimentally with excellent results.
Keywords: enantioselective extraction – 4-nitro-phenylalanine – equilibrium formation – BINAP – modelling
Full paper is available at www.springerlink.com.
Chemical Papers 68 (1) 80–89 (2014)