Imidazolium-based Ionic Liquid Microemulsion And Its Applications In Biocatalysis

Ionic liquid is a new media and soft-function material which isdeveloping under the framework of the green chemistry in the recent20years. Because of its special solvent properties, it is applied to theindustrial product as green solvent in green chemistry. Themicroemulsion is a new type media effectively used in biologicalcatalysis. So exploring the ionic liquid microemulsion used in biologicalcatalysis is of a great potential value. The formations of microemulsionswith ionic liquids were studied in this paper and the microemulsions wereapplied in the enantioselective transesterification of racemicp-bromo-phenylpropanol by lipase, in which the lipase can keep theperfect enantioselectivity. The work was carried out as follows:Firstly, five kinds of1,3-dilkylimidazolium-based ionic liquids weresynthesized including [BMIM][BF4],[BMIM][PF₆],[EMIM][PF₆],[HMIM][PF₆],[OMIM][PF₆]. The transesterification of racemicp-bromo-phenylpropanol by lipase was chosen as the model reaction tostudy on effects of the reaction medium, water content, pH, temperatureand shaking speed on the reaction. The optimizations conditions forlapase activity were at about pH7.0and temperature30oC.Secondly, microemulsions with ionic liquids were constructed andthe phase behaviors was studied. The results suggested that the transparent microemulsions were formed by several kinds of alkane withsurfactants （TX-100, Tween85and Tween80） and [BMIM][BF4] whichreplaced the water component, while the microemulsion was not formedusing another ionic liquid--hydrophobic ionic liquid [BMIM][PF₆]. Thedifferent cosurfactants used to construct microemulsion also were studied.From the phase behaviour investigation, comparing to1-propanol and1-pentanol notable magnification of the single-phase region was revealedby using butanol. The optimical R （R:weight ratio of the cosurfactant andsurfactant） was different in the different systems.Thirdly, transesterification reactions of racemic p-bromo-phenyl-propanol by lipase were carried out in the three microemulsions asreaction solvents. Also, the esterification of stability in the microemulison[BMIM][PF₆]/TX-100+1-butanol （1:1） was studied in this paper.Finally, the reaction kinetics of tansesterifiation was establishedaccording to the transesterification reaction of racemicp-bromo-phenylpropanol by lipase in above reaction medium. Thekinetics equation was as below:In a word, some valuble results were obtained through the behaviorsof ionic liquid microemulsions and its application in enzyme catalysis.All those results might be beneficial to advance researching using thesystems of microemulsions with ionic liquids.