Equilibrium Studies On Enantioselective Liquid-liquid Extraction Of α-amino Acids Enantiomers Using Metal-BINAP Complexes

In the thesis, enantioselective liquid-liquid extraction of α-amino acidsenantiomers was investigated with metal-BINAP complexes as enantioselectiveextractants. We have investigated the influence of a number of process variables onefficiency of the extraction, such as types of metal precursors and organic solvents,pH of the aqueous phase, concentration of extractant, and temperature. Depending onthe solubility of α-amino acids in the organic phase, physical partition, acid-basedissociation equilibrium, equilibrium of ligand exchange reaction and extractionmechanisms, we will apply the homogeneous ligand addition mechanism and/or theinterfacial ligand exchange mechanism for model of these reactive extraction system.We can use the models to predict the extraction performance quantitatively and themodels also provide a simple computational approach to process optimization. Thebest conditions were obtained by experiments and modeling and optimization. Themain results of experiments as follows:(1)(CH3CN)4CuPF6is chosen as the suitable metal precursor for the extractionof phenylalanine (Phe) enantiomers, the extractant (BINAP-Cu complex) has thehighest discrimination ability for Phe enantiomers. When BINAP-Cu complex is usedas an extractant, L-Phe is the preferred enantiomer. We have applied the interfacialreaction model in the extraction system. A comparison of the experimental real valueswith the values of simulation indicates that the values of simulation is consistent withexperimental data well and the interfacial reaction model can be used for simulationand optimization of the reactive extraction. The best conditions involve BINAP-Cucomplex concentration of2mmol/L in1,2-dichloroethane, and a pH value of7at5oCwas obtained by experiments and model. The highest enantioselectivity is5.2038.(2)(CH3CN)4CuPF6is chosen as the suitable metal precursor for the extractionof homophenylalanine (Hph) enantiomers, the extractant (BINAP-Cu complex) hasthe highest discrimination ability for Hph enantiomers. D-Hph is the preferredenantiomer when extracted by palladium or nickel BINAP complexes, but usingcopper-BINAP complex as selector, L-Hph is the preferred enantiomer. We haveapplied the homogeneous ligand addition mechanism and the interfacial ligandexchange mechanism respectively for model in the extraction system. Comparisonbetween the experimental values and the values calculated by the two differentmodels indicates that the homogeneous reaction model can predict more accurately. By modeling and experiment, the best condition concerning BINAP-Cu complexconcentration of2mmol/L in1,2-dichloroethane, and a pH value of8at5oC wasobtained.(3)(CH3CN)4CuPF6is chosen as the suitable metal precursor for the extractionof valine (Val) enantiomers, the extractant (BINAP-Cu complex) has the highestdiscrimination ability for Val enantiomers. When BINAP-Cu complex is used as anextractant, L-Val is the preferred enantiomer. We have applied the interfacial reactionmodel in the extraction system. Comparison betweent the experimental values of theextraction experiment of Val and the values calculated by the interfacial reactionmodel indicates that the interfacial reaction model is fit the extraction system. Thebest conditions involve BINAP-Cu complex concentration of2mmol/Lindichloromethane, and a pH value of8at5oC was obtained by experiments andmodel.(4) PdCl2(CH3CN)2is chosen as the suitable metal precursor for the extraction of4-chlorophenylglycine (Pcpg) enantiomers, the extractant (BINAP-Pd complex) hasthe highest discrimination ability for Pcpg enantiomers. We have applied theinterfacial reaction model in the extraction system. A comparison of the experimentalvalues of the extraction experiment of Pcpg with the predictions of interfacial reactionmodel indicates that the interfacial reaction model can fit the extraction system whenthe pH is lower than8.0. The best conditions involve pH of7and the host (BINAP-Pdcomplex) concentration of1mmol/L in chloroform at5oC was obtained.