Abstract
To meet the demands of some kinds of reactions catalyzed simultaneously by Br?nsted acid and Lewis acid catalyst, two novel Br?nsted-Lewis acidic ionic liquids, 1-carboxyethylene-3-(4-zinc acetate sulfobutyl) imidazolium chloride ([CH3COO-Zn-O3S-bim-CH2CH2COOH]Cl) and 1-(1,2-dicarboxy) ethylene-3-(4-zinc acetate sulfobutyl) imidazolium chloride ([CH3COO-Zn-O3S-bim-C4H5O4]Cl) were synthesized, in which both Br?nsted and Lewis acidic sites existed in the cation. The structures of the ionic liquids were determined by means of FT-IR, 1H NMR and elemental analysis. The results of Py-IR analysis indicated that the two novel ionic liquids have both Br?nsted and Lewis acid properties. The acid strength values (H0) of the ionic liquids were measured utilizing the UV-visible spectroscopy combined with Hammett indicator method, and the acid amount of them was determined by acid-base titration.
Highlights
Ionic liquids, due to their strong dissolving capacity, negligible vapor pressure, high thermal and chemical stability, have attracted much attention
To meet the demands of some kinds of reactions catalyzed simultaneously by Brønsted acid and Lewis acid catalyst, two novel Brønsted-Lewis acidic ionic liquids, 1-carboxyethylene-3-(4-zinc acetate sulfobutyl) imidazolium chloride ([CH3COO-Zn-O3S-bim-CH2CH2COOH]Cl) and 1-(1,2-dicarboxy) ethylene-3-(4-zinc acetate sulfobutyl) imidazolium chloride ([CH3COO-Zn-O3S-bim-C4H5O4]Cl) were synthesized, in which both Brønsted and Lewis acidic sites existed in the cation
The structures of BLILs-1 and BLILs-2 were characterized by IR, 1H NMR and Elemental analysis, and the results indicated that the structures of the Brønsted-Lewis acidic ionic liquids synthesized in this work were corresponding to those of the target products
Summary
Due to their strong dissolving capacity, negligible vapor pressure, high thermal and chemical stability, have attracted much attention. Chloroaluminate ionic liquid is sensitive to moisture and unstable, so FeCl3 or other metal halide gradually takes the place of AlCl3 to prepare Lewis acidic ionic liquids which are not sensitive to water [1]. Liu et al [5,6] synthesized a Brønsted-Lewis acidic ionic liquid [HSO3-(CH2)3-NEt3]ClZnCl2 and evaluated its catalytic performance in rosin dimerization and fatty acid methyl ester dimerization, respectively. They [7,8,9] prepared another Brønsted-. Publications about the synthesis of Brønsted-Lewis acidic ionic liquids with both Brønsted and Lewis acidic sites in the cation have been reported. Two novel Brønsted-Lewis acidic ionic liquids with both Brønsted and Lewis acidic sites in the cation were prepared first, and their structures and acidity were characterized
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