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Different Ionic Liquids (different + ionic_liquid)
Selected AbstractsChirality Transfer in Imidazolium Camphorsulfonate Ionic Liquids through Ion Pairing EffectsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Karola Schneiders Abstract The paper describes our studies on ion pair interactions in ionic liquids (IL) using an asymmetric hydrogenation reaction as probe. Three different ionic liquids carrying prochiral keto-functionalized cations were hydrogenated in the presence of their chiral, enantiomerically pure counter-ion using an achiral heterogeneous ruthenium catalyst. For the hydrogenation of N -(3,-oxobutyl)- N -methylimidazolium camphorsulfonate (2), N -(3,-oxobutyl)imidazolium camphorsulfonate (4) and N -(5,-oxohexyl)- N -methylimidazolium camphorsulfonate (6) we found a strong dependency of the enantiomeric excess (ee in the cation) on the polarity of the solvent, the concentration of the IL and the structure of the IL. The highest ee values of up to 94% were found for the hydrogenation of 2 in ethanol. Interestingly, we observed that the ee (and consequently the strength of ion pair interaction) had a pronounced maximum for a certain concentration of the IL in the solvent depending on the nature of the solvent and on the substrate. Remarkably, the concentration leading to the maximum ee could be rationalized by independent determination of the degree of dissociation which was obtained by a combination of diffusion-ordered NMR spectroscopy and conductivity measurements. [source] Which Controls the Depolymerization of Cellulose in Ionic Liquids: The Solid Acid Catalyst or Cellulose?CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 2 2010Roberto Rinaldi Dr. Abstract Cellulose is a renewable and widely available feedstock. It is a biopolymer that is typically found in wood, straw, grass, municipal solid waste, and crop residues. Its use as raw material for biofuel production opens up the possibility of sustainable biorefinery schemes that do not compete with food supply. Tapping into this feedstock for the production of biofuels and chemicals requires,as the first-step,its depolymerization or its hydrolysis into intermediates that are more susceptible to chemical and/or biological transformations. We have shown earlier that solid acids selectively catalyze the depolymerization of cellulose solubilized in 1-butyl-3-methylimidazolium chloride (BMIMCl) at 100,°C. Here, we address the factors responsible for the control of this reaction. Both cellulose and solid acid catalysts have distinct and important roles in the process. Describing the depolymerization of cellulose by the equivalent number of scissions occurring in the cellulosic chains allows a direct correlation between the product yields and the extent of the polymer breakdown. The effect of the acid strength on the depolymerization of cellulose is discussed in detail. Practical aspects of the reaction, concerning the homogeneous nature of the catalysis in spite of the use of a solid acid catalyst, are thoroughly addressed. The effect of impurities present in the imidazolium-based ionic liquids on the reaction performance, the suitability of different ionic liquids as solvents, and the recyclability of Amberlyst 15DRY and BMIMCl are also presented. [source] Gas Phase Conversion of Carbon Tetrachloride to Alkyl Chlorides Catalyzed by Supported Ionic LiquidsCHINESE JOURNAL OF CHEMISTRY, Issue 9 2009Aijun Sun Abstract An efficient way of converting carbon tetrachloride (CTC) to alkyl chlorides is reported, which uses the catalysts of ionic liquids supported on granular active carbon. The catalytic performance was evaluated in a temperature range of 120,200°C and atmospheric pressure for different ionic liquids, namely 1-butyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, hydrochloric salts of N- methylimidazole (MIm), pyridine and triethylamine, as well as bisulfate and dihydric phosphate of N- methylimidazole. On this basis, the reaction mechanism was proposed, and the influences of the reaction temperature and the attributes of ionic liquids were discussed. The overall reaction was assumed to be comprised of two steps, the hydrolysis of CTC and reaction of HCl with alcohols under acidic catalyst. The results indicate that the conversion of CTC increased monotonically with temperature and even approached 100% at 200°C, while the maximum selectivity to alkyl chlorides was obtained around 160°C. This reaction might be potentially applicable to the resource utilization of superfluous byproduct of CTC in the chloromethane industry. [source] A Mild and Efficient Synthesis of 5-Oxo-5,6,7,8-tetrahydro-4H -benzo-[b]-pyran Derivatives in Room Temperature Ionic LiquidsCHINESE JOURNAL OF CHEMISTRY, Issue 8 2005Jiang Zhao-Qin Abstract A one-pot synthesis of a series of 5-oxo-5,6,7,8-tetrahydro-4H -benzo-[b]-pyran derivatives via three-component coupling reactions of aldehydes, dimedone and malononitrile in room temperature ionic liquids (RTILs) without any catalyst has been reported. In the meantime, the reuse of ionic liquids and the effect of different ionic liquids as solvent on the reaction have also been investigated. [source] | ||||||||||