Chiral Material Identification And Inclusion Interaction Of The Alcohol / Salt Aqueous Two-phase System

In this paper, mandelic acid(MA) enantiomers andα-cyclohexyl-mandelic acid (CHMA) enantiomers were separated by a novel chiral separation extraction systems-Alcohol/salt-based aqueous two-phase systems(ATPSs). The main contents can be summarized as follows:The first,the screening study of chiral recognition ability for cyclodextrins group reagents in the alcohol/salt-based aqueous two-phase system:Chiral recognition of mandelic acid and a-cyclohexyl-mandelic acid by alcohol/salt-based aqueous two-phase systems(C2H5OH/(NH4)2SO4,C2H5OH/K2HPO4,n-C3H7OH/(NH4)2SO4,n-C3H7OH/K2HPO4,i-C3H7OH/(NH4)2SO4,i-C3H7OH/K2HPO4) containing chiral selector(P-cyclodextrin,hydroxypropyl-β-cyclodextrin,hydroxypropyl-a-cyclodextrin,sulfonated-β-cyclodextrin,water-soluble (3-cyclodextrin polymer). The experimental results indicate that only P-cyclodextrin and hydroxypropyl-β-cyclodextrin as chiral selector showed a good chiral recognition ability toward CHMA enantiomers. Sulfonated-β-cyclodextrin have a chiral recognition ability toward MA enantiomers. It was also found that β-cyclodextrin and hydroxypropyl-β-cyclodextrin only have a chiral recognition ability in the C2H5OH/(NH4)2SO4 system. Sulfonated-β-cyclodextrin also only have a chiral recognition ability in the C2H5OH/(NH4)2SO4 system.The second,the dependency of the distribution ratio (D) and the separation factors(α) on parameters, such as the concentration of HP-β-CD,the concentration of CHMA, the mass fractions of C2H5OH and (NH4)2SO4 respectively,temperature and pH have been investigated. It could be concluded that the enantioseparation strongly depended on the concentration of HP-β-CD,the mass fraction of C2H5OH,temperature and pH. The optimum conditions of enantioseparation were as follows:The temperature was 40℃,the pH was 2.0,the mass fraction of C2H5OH and (NH4)2SO4 was 30%and 15%, respectively,the concentration of HP-β-CD was 50 g.L-1 the concentration of CHMA was 0.5 mmol.L"1.Under these conditions the separation factor(a) reached at 1.86. The third,the dependency of the distribution ratio (D) and the separation factors(a) on parameters such as the concentration of S-β-CD,the concentration of CHMA, the mass fractions of C2H5OH and (NH4)2SO4respectively,temperature and pH have been investigated. The maximum enantioselectivity(a=1.65, e.eup=15.7%) was reached by employing S-P-CD(Ⅱ) as chiral selector in the ethanol/ammonium sulfate system.The forth,the study of chiral recognition ability for Cu2-β-CD in the alcohol/salt-based aqueous two-phase system:Firstly,The dinuclear Cu2-β-CD complex was synthesized and characterized by IR,UV,XRD. The chiral recognition system was established by adding Cu2-β-CD into the alcohol/salt-based aqueous two-phase system. The experimental results show that the C2H5OH/(NH4)2SO4 and i-C3H7OH/(NH4)2SO4 aqueous two phase extraction system containing Cu2-β-CD has well chiral recognition ability toward CHMA enantiomers.Then,the dependency of the distribution ratio (D) and the separation factors(a) on parameters such as the concentration of Cu2-β-CD, the mass fractions of C2H5OH and (NH4)2SO4 respectively,temperature and pH were investigated. The experimental results indicate that the optimum conditions of enantioseparation were as follows:The temperature, was 30℃,the pH was 6.0,the mass fraction of C2H5OH and (NH4)SO4 was 35% and 15%, respectively,the concentration of Cu2-β-CD was 20 mmol.L-1,the concentration of CHMA was 0.5mmol.L-1.Under these conditions the separation factor(a) reached at 1.47.The fifth,the inclusion behavior between HP-β-CD and CHMA,S-β-CD and MA,Cu2-p-CD and CHMA was studied by infrared spectroscopy.The results indicate that the characteristic peak of-C=O group of CHMA in its inclusion compound of HP-β-CD/CHMA shifted from 1728 cm-1 to 1715 cm-1,the characteristic peak of-C=O group of CHMA disappeared in the infrared spectra of the inclusion compound of Cu2-β-CD/CHMA, the characteristic peak of-C=O group of MA in its inclusion compound of S-β-CD-MA shifted from 1728cm-1 to 1715 cm-1.The infrared spectra indicate that HP-P-CD and CHMA, S-β-CD and MA,Cu2-β-CD and CHMA all form the inclusion compound.