The Design,Synthesis And Characterization Of The Amino Acid-based Chiral Ionic Liquids

Ionic liquids(ILs)have been considered to be environmental friendly solvents in recent years because of their unique physical and chemical properties,such as negligible vapour pressures,a high solvating capacity for both polar and non-polar compounds,high thermal stability,high ionic conductivity,nonflammability,and large liquid-state temperature range.Due to the chiral recognition ability,the researchers gradually pay close attention to chiral ionic liquids(CILs).For example,the CILs are used as the chiral agent and chiral solvents in the enantiomer extraction separation.In the other fields,the CILs also play an important role,such as asymmetric organic synthesis,spectroscopy in the NMR,NIR,fluorescence,chromatography in the GC,HPLC,MCE,CE,and so on.What's more,the CILs could also be used as the liquid crystal materials.Because of the low cast and the abundant chiral pools,and the biorenewable and biodegradable of chiral ionic liquids based on the amino acids,a few series of amino acid-based chiral ionic liquids(AAILs),derived from of the L-leucine and L-aspartic,are to be designed,and synthesized.The structure-activity relationship between AAILs and the specific rotation was studied.The research found that with the increase of the alkyl chain on the amine groups,it is more difficult to synthesize the AAILs,and the change of the anions can affect the viscosity of the AAILs.When the difference of the alkyl chains on the AAILs become more obvious,the specific rotation of the AAILs is more larger,and the specific rotation can be effected by the fefferent anion,solvent.The N K-edge energy of AAILs and imidazole ILs were same with 401.1 eV detected by XANES,indicating that the substituent group of imidazole and anion had no effect on the energy of N in the imidazole.Besides,the N K-edge energy of synthesized AAILs hold at 405.6 eV with different carbon chains,amino acids and anions,same with the achiral quaternary ammonium compounds,which proved that modified N in quaternary ammonium salt were all same without effect of other conditions.