Synthesis And Characterization Of Novel Brφnsted-lewis Acidic Ionic Liquids

The synthesis of new functionalized ionic liquids is one of the research focuses in the field of ionic liquids recently. A series of Br?nsted-Lewis acidic functionalized ionic liquids were prepared and their structures, acid property and thermal stability were determined. Four mixed type Br?nsted-Lewis acidic ionic liquids (SFILs) ([HSO3-b-N-(C2H5)3]Cl- ZnCl2) were prepared, and their structures were determined by means of FT-IR. The Br?nsted acidic sites exist in the cation and the Lewis acidic sites emerges in the anion in these ionic liquid molecules. The Br?nsted and Lewis acidity of the SFILs was confirmed by FT-IR using pyridine as a probe molecule. When the molar fraction of ZnCl2 was less than 0.5, the SFILs possessed only Br?nsted acidity and otherwise, the SFILs showed Br?nsted–Lewis acidity. The acidic amounts of the SFILs was determinated by acid-base titration. The acid strength of the SFILs was determined by the Hammett method combined with UV-visible spectroscopy, and the result indicated that the H0 of SFILs-I and SFILs-IV was 2.0 and 1.6. A novel Br?nsted-Lewis acidic ionic liquids ([CH3COO-Zn-O3S-bim- CH2CH2COOH]Cl, SFILs-V) was prepared in which both Br?nsted and Lewis acidic sites exist in the cation. The structure of SFILs-V was determined by means of FT-IR, 1H-NMR, ESI-MS and elemental analysis, and was confirmed as follows: The acid amount of the SFILs determinated by acid-base titration was 2.0 mol NaOH / mol SFILs-V. The acid strength of the SFILs was determined by the Hammett method combined with UV-visible spectroscopy ,and the result indicated that the H0 of SFILs-V was 5.6. The thermal stability of SFILs-V was tested by means of thermogravimetric analysis and the result showed that the initial thermal decomposition temperature was 260℃and its liquid range was 80~260℃.