Synthesis, Characterization And Properties Research Of The Ester-base Imidazoles Ionic Liquids

Room temperature ionic liquids (ILs) have many unique physicochemicalproperties, such as negligible volatility, high thermal stability, strong solubility andfine-tuning ability for the physical and chemical properties.Thus ILs have been usedin chemical synthesis, catalysis, extraction and separation science and materialpreparation.As the theory of ionic liquids develop, design and develop ionic liquids withspecial function for specific requirement become more and more meaningful. Themajor content of the paper is as follows：(1) According to the representative compounds of SVOCs in indoor air(bis(2-Ethylhexyl) phthalate,and2,2’,4,4’-Tetrabromodiphenylether, five newselective imidazolium ionic liquids with ester base functional groups are synthesizedby two-step method, namely,[MIMCH2COOCH3]NTf2、[MIMCH2COOCH2CH3]NTf2、[MIMCH2COOCH2CH2CH3]NTf2、[MIMCH2C6H4COOCH3]NTf2and [MIMCH2C6H4COOCH2CH3]NTf2。(2) These ionic liquids are characterized by ultraviolet spectrum, infraredspectrum, nuclear magnetic and mass spectrometry.The compositions and structuresof the ionic liquids are confirmed. And they are also determined by elemental analysisand the results of C, H, N content are in line with the theoretical values.(3) The physical and chemical properties of the five ionic liquids are investigated,including solubility, thermal stability, electrochemical window and conductivity.Theresults show that the solubility of the ionic liquids in organic solvent is associatedwith the polarity of the solvent. The solubility of the ionic liquids in water,tetrachloromethane and n-hexane is nearly none. As the length of the cationicsubstituent on the ionic liquids increases, the initial decomposition temperaturegradually decreased; the electrochemical window of the five kinds of ionic liquids areabout3v.The temperature, concentration and the kinds of solvents all have effects onthe conductivity of the ionic liquid. The conductivity increases with temperatureincreasing, the conductive ability of the ionic liquid is associated with the solvent, inthe experimental range of the concentration, the conductivities of the ionic liquids areincreased with the increasing of the concentration.(4) The thermodynamic parameters of the ionic liquids [BMIM]NTf2,[MIMCH2COOCH2CH3]NTf2,[MIMCH2COOCH2CH2CH3]NTf2and [MIMCH2C6H4COOCH2CH3] NTf2are obtained by gas chromatography. The resultsshow①on the same chromatographic column, the specific retention volumes of themolecular probes decrease as the increase of the temperature.②The activitycoefficients at infinite dilution of the alkanes are higher than10and are bad solventsfor the investigated ionic liquids, but ethyl acetate and2-pentanone are good solventsfor the ionic liquids.③The molar enthalpy of vaporization of the alkanes increasewith the increasing of the length;all probe molecules dissolved in ionic liquidstationary phase are spontaneous exothermic process; probe alkanes and methanolmixed with ionic liquid in infinite dilution are endothermic process, and ethyl acetateand2-pentanone mixed with ionic liquid in infinite dilution are exothermicspontaneous process.④The Flory-Huggins interaction parameters between probemolecules and ionic liquids change with the increasing of the temperature.⑤Thesolubility parameter data show that the researched ionic liquids are proton supplybodies also are proton acceptors, and the ability to provide proton stronger than theability to accept protons.(5)By comparing chromatography, the commercial1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide([BMIM]NTf2) and five ionic liquids which aredesigned and synthesized by ourselves, are chosen as the stationary phase respectively.The results show that the ionic liquid [MIMCH2COOCH3]NTf2probably has thewide application in our further research in the future.