The Synthesis Of Amino Acid Ester-based Ionic Liquids And Their Separation Performance

As a potential "green" solvent, ionic liquids are attracting the attention of a growing number ofscientists and engineers in recent years. At present, most of the researches reported in literature werefocused on the imidazole-based ionic liquids. However, many of these ionic liquids are harmful toorganisms and environment. Therefore, developing non-toxic and harmless ionic liquids is the premise toachieve green appilication of ionic liquids. As a part of the project supported by the Key Programme ofNational Natural Science Foundation of China (No.21133009), a series of amino acid ester-based ionicliquids have been synthesized and characterized, and the phase behavior of ionic liquids-water has beenstudied. Moreover, some of the ionic liquids were used for the extraction of coumarins, purine alkaloidsand amino acids from aqueous solutions. The effects of sturetures of the ionic liquids and the drugmolecules as well as temperature of the systems on the partitioning are also investigated. The main contentsof the works are as follows.1.15kinds of ionic liquids based on bis(trifluoromethane sulfonimide) anion ([Tf₂N]-) and amino acidderivatives cations have been synthesized using an easy preparation way and characterized by DSC, TGAand NMR techniques. The amino acid derivatives cations include the cations of glycine ethyl ester, alanineethyl ester, serine ethyl ester, valine methyl ester, valine ethyl ester, leucine methyl ester, leucine ethyl ester,glycine benzyl ester, phenylglycine methyl ester, phenylalanine methyl ester, phenylalanine ethyl ester,tryptophan ethyl ester, tyrosine methyl ester, Hydroxyproline methyl ester, aspartic acid dimethyl ester.2. The liquid-liquid phase diagram of valine methyl ester bis(trifluoromethane sulfonimide)-water andvaline ethyl ester bis(trifluoromethane sulfonimide)-water systems has been determined, and the effect oftemperature on microscopic structure of the ionic liquid-water systems has been inveatigated by DLS andNMR techniques.3. The partition coefficients of the coumarin derivatives drugs (coumarin,4-hydroxycoumarin,7-hydroxycoumarin, coumarin-3-carboxylic acid,6,7-dihydroxycoumarin,3-aminocoumarin and6,7-dihydroxy-4-methylcoumarin) in the hydrophobic amino acid ester-based ionic liquids weredetermined, and the effects of molecular structures of the ionic liquids and the coumarins as well as temperature of the systems on the partitioning of coumarins were examined. A green separation processbased on hydrophobic amino acid ester-based ionic liquids was proposed.4. The partition behavior of purine alkaloids (caffeine, theobromine, theophylline,2,6-amino purine,inosine) in the hydrophobic amino acid ester-based ionic liquids were studied. The effects of temperatureof the systems and molecular structures of the ionic liquids and purine alkaloids on the partitioning ofpurine alkaloids were examined, and the possible extraction mechanism has been investigated from¹³CNMR measurements.5. The partition behaviors of L-Tryptophan, L-phenylalanine and L-Tyrosine in the amino acidester-based ionic liquids-water systems were determined. The effects of pH of the systems and molecularstructure of the ionic liquids and amino acids on the partitioning of amino acids were examined.