- Solvation structure and dynamics of Li+ in Lewis-basic ionic liquid of 1-octyl-4-aza-1-azoniabicyclo[2.2.2]octane bis(trifluoromethanesulfonyl)amide
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1H, 7Li, 13C, 15N, and 19F NMR spectra of 1-octyl-4-aza-1-azoniabicyclo[2.2.2]octane bis(trifluoromethanesulfonyl)amide ([C8dabco][TFSA]) solutions with and without LiTFSA (lithium mole fractions of xLi = 0 and 0.1) were measured at 313.2 K. The chemical shift measured for each nucleus was corrected for volume magnetic susceptibility of the solution. For comparison, those NMR spectra of 1-methyl-3-octylimidazolium bis(trifluoromethanesulfonyl)amide ([C8mim][TFSA]) solutions were recorded under the same condition. The peak shifts for the nuclei induced by the dissolution of Li+ showed that Li+ interacts with not only TFSA- but also C8dabco+ in [C8dabco][TFSA] solution. Self-diffusion coefficients of the cation, anion, and Li+ in the ionic liquid solutions were determined by a pulsed field gradient NMR technique. Correlation times for jump motion of Li+ were estimated from 7Li longitudinal relaxation times with two different magnetic fields. The diffusion and jump motions of Li+ in [C8dabco][TFSA] and [C8mim][TFSA] solutions are discussed in terms of interionic interactions.
- Umecky, Tatsuya,Suga, Kenta,Masaki, Eiji,Takamuku, Toshiyuki,Makino, Takashi,Kanakubo, Mitsuhiro
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- Liquid-liquid equilibria for [C8mim][NTf2] + thiophene + 2,2,4-trimethylpentane or + toluene
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Tie-line compositions for type II systems of 1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide + thiophene + 2,2,4-trimethylpentane or + toluene have been determined at 298.15 K and atmospheric pressure. Solute distribution coefficient and selectivity values have also been determined. The experimental data were correlated with the NRTL and UNIQUAC equations. The best results were found with the UNIQUAC equation. The NRTL equation could not adequately correlate the system with toluene.
- Alonso, Luisa,Arce, Alberto,Francisco, Maria,Soto, Ana
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- Cross-linked polymer-ionic liquid composite materials
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A series of composites, some with permanent porosity, comprising polymers and ionic liquids have been prepared by in-situ polymerization. The characteristics of both composites and isolated polymers have been investigated. Slow mass and phase transfer characterize the interaction with a range of polymers (1-17) in the N,N′-dialkylimidazolium liquids, [emin]BF4, [bmim]PF6, or [omim]N(SO2CF3)2. Free-radical homopolymerization of 1-vinyl-2-pyrrolidinone in [bmim]PF6 or of 4-vinylpyridine in [omim]N-(SO2CF3)2 gave viscous solutions from which polymer (Mw = 162 500 and 71 500 g mol-1, respectively) could be isolated. Detectable ionic liquid residues were retained in the isolated polymers despite five reprecipitations from methanol. Copolymerization of 4-vinylpyridine (VP) with 5% divinylbenzene (DVB) or trimethylolpropane trimethacrylate (TRIM) in [omim]N(SO2CF3)2, and homopolymerizations of the cross-linking monomes on their own, led with 90-100% monomer conversion to a series of gel-like composite materials, B-H, from which gross-linked polymers, B′-H′, could be isolated by Soxhlet extraction of the ionic liquid. Copolymers of VP with 5-30% DVB (E′, F′) showed a low degree of permanent porosity in the dry state. However, poly(DVB) (G′) and poly(TRIM) (H′) have bulk densities (-3), intrusion volumes (>0.9 cm3 g-1), BET surface area (70-320 m2 g-1), and morphology (from SEM studies) which demonstrate the porogenic character of the ionic liquids used. Comparisons with the related products I and J obtained in toluene reveal the sensitivity of these systems both to the properties of the porogen solvent and to the monomer used.
- Snedden, Peter,Cooper, Andrew I.,Scott, Keith,Winterton, Neil
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- Synthesis and properties of seven ionic liquids containing 1-methyl-3-octylimidazolium or 1-butyl-4-methylpyridinium cations
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Syntheses are reported for ionic liquids containing 1-methyl-3- octylimidazolium or 1-butyl-4-methylpyridinium cations and trifluoromethyl sulfonate, dicyanamide, bis(trifluoromethylsulfonyl)imide, or nonafluorobutyl sulfonate anions. Densities, melting points, glass-transition temperatures, solubilities in water, and polarities have been measured. Ionic liquids containing pyridinium cations exhibit higher melting points, lower solubility in water, and higher polarity than those containing imidazolium cations.
- Papaiconomou, Nicolas,Yakelis, Neal,Salminen, Justin,Bergman, Robert,Prausnitz, John M.
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- Physical properties of binary and ternary mixtures of ethyl acetate, ethanol, and 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide at 298.15 K
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Densities, viscosities, and refractive indices for binary and ternary mixtures of ethanol, ethyl acetate, and l-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide have been determined at 298.15 K and atmospheric pressure. Excess molar volumes, and viscosity and molar refraction changes of mixing have been calculated from the measured physical properties. These changes of mixing have been adequately fitted to the Redlieh - Kister polynomial equation. The adjustable parameters and the standard deviations between experimental and calculated values are reported.
- Andreatta, Alfonsina E.,Arce, Alberto,Rodil, Eva,Soto, Ana
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- Synthesis and characterization of nickel nanoparticles dispersed in imidazolium ionic liquids
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The diameter and size-distribution of Ni nanoparticles prepared by the decomposition of [bis(1,5-cyclooctadiene)nickel(0)] organometallic precursor dissolved in 1-alkyl-3-methylimidazolium N-bis(trifluoromethanesulfonyl) amide ionic liquids depend on the length of the alkyl side-chain of the imidazolium ring. The increase of the organization range order of the ionic liquid that increases with that of the alkyl side-chain (from n-butyl to n-hexadecyl) induces the formation of nanoparticles with a smaller diameter and size-distribution. The cubic fcc Ni nanoparticles with 4.9 ± 0.9 to 5.9 ± 1.4 nm in mean diameter and monomodal size-distribution thus prepared are probably composed of a small cap layer of NiO around a core of Ni metal. The contribution of the oxide layer also depends on the medium i.e. the metal oxide ratio increases in salts containing four to eight carbons on their side-chains and then decreases as the number of carbons increases. The Ni nanoparticles dispersed in the ionic liquids are active catalysts for the hydrogenation of olefins under relatively mild reaction conditions. the Owner Societies.
- Migowski, Pedro,Machado, Giovanna,Texeira, Sergio R.,Alves, Maria C. M.,Morais, Jonder,Traverse, Agnes,Dupont, Jairton
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- Solubility of CO2, H2S, and their mixture in the ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethyl)sulfonylimide
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Gaseous solubilities of carbon dioxide (1), hydrogen sulfide (2), and their binary mixture (x2 ≈ 0.2, 0.5, 0.8) have been measured in the ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethyl)sulfonylimide ([C8mim][Tf2N]) at temperatures ranging from (303.15 to 353.15) K and at pressures under 2 MPa. The observed PTx solubility data were used to obtain Henry's law constants and correlated by three models: (1) the simple Krichevsky-Kasarnovsky (KK) equation, (2) a model comprised of the extended Henry's law and the Pitzer's virial expansion for the excess Gibbs free energy, and (3) the generic Redlich-Kwong (RK) cubic equation of state proposed for gas-ionic liquid systems. The correlations from the three models show quite good consistency with the experimental data for IL/CO2 and IL/H 2S binary mixtures within experimental uncertainties. For IL/CO 2/H2S ternary mixtures, the RK model shows the best correlation with the experimental data. The comparison showed that the solubility of H2S is about two times as great as that of CO 2 in the ionic liquid studied in this work. It was further found, by comparison of the experimental data of this study with those of previous reports, that the solubility of H2S in [Cnmim][Tf 2N] ILs increases as the number of carbon atoms in the alkyl substituent of methylimidazolium cation, n, increases. In addition, quantum chemical calculations at DFT/B3LYP level of theory using 6-311+G(d) and 6-311++G(2d,2p) basis sets were performed on the isolated systems studied in this work to provide explanations from a molecular point of view for the observed experimental trends.
- Jalili, Amir Hossein,Safavi, Mohammadali,Ghotbi, Cyrus,Mehdizadeh, Ali,Hosseini-Jenab, Masih,Taghikhani, Vahid
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- Nanoreactors stable up to 200 °c: A class of high temperature microemulsions composed solely of ionic liquids
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It is a challenge to develop microemulsions which can serve as nanoreactors for the synthesis of nanoparticles and chemical reactions at high temperature. In this work, a class of novel high temperature microemulsions consisting solely of ionic liquids have been designed and prepared for the first time. It is found that nanoscale droplets formed in the ionic liquid microemulsions can be maintained up to 200 °C, and the size distribution of the droplets can be easily tuned by selection of the ionic liquids and varying compositions of the systems. By using such microemulsions as nanoreactors, porous metals such as Pt have been prepared at 180 °C without using any purposely added reductant.
- Pei, Yuanchao,Ru, Jie,Yao, Kaisheng,Hao, Lihui,Li, Zhiyong,Wang, Huiyong,Zhu, Xingqi,Wang, Jianji
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supporting information
p. 6260 - 6263
(2018/06/22)
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- Anion Analysis of Ionic Liquids and Ionic Liquid Purity Assessment by Ion Chromatography
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The simultaneous determination of halide impurities (fluoride, chloride, bromide, and iodide) and ionic liquid (IL) anions (tetrafluoroborate, hexafluorophosphate, and triflimide) using ion chromatography was developed with a basic, non-gradient ion chromatography system. The non-gradient method uses the eluent Na2CO3/NaHCO3in water/acetonitrile (70:30 v:v) on the AS 22 column to enable a rapid and simultaneous analysis of different IL and halide anions within an acceptable run-time (22 min) and with good resolution R of larger than 2.4, a capacity k′ between 0.4 and 5.1, selectivities α between 1.3 and 2.1, and peak asymmetries Asof less than 1.5. Halide impurities below 1 ppm (1 mg·L–1of prepared sample solution) could be quantified. A range of ionic liquids with tetrafluoroborate [BF4]–, hexafluorophosphate [PF6]–, and bis(trifluoromethylsulfonyl)imide (triflimide) [NTf2]–anions combined with cations based on imidazole, pyridine, and tetrahydrothiophene could be analyzed for their anion purity. The IL-cations do not influence the chromatographic results. With the analysis of 18 ILs differing in their cation-anion combination we could prove the general applicability of the described method for the anion purity analysis of ionic liquids with respect to halide ions. The IL-anion purity of most ILs was above 98 wt %. The highest IL-anion purity was 99.8 wt %, implying anion impurities of only 0.2 wt %. The used halide anion from the synthesis route was the major anion impurity, yet with chloride also bromide and fluoride (potentially from hydrolysis of [BF4]–) were often detected. When iodide was used, at least chloride but sometimes also bromide and fluoride was present. However, even if the IL-anion content is above 99 wt %, it does not necessarily indicate an ionic liquid devoid of other impurities. From the IC analysis, one can also deduce a possible cation impurity if one takes into account the expected (calculated) IL-anion content. A matching experimental and theoretical IL-anion content excludes, a higher experimental content indicates the presence of residual KBF4, NH4PF6, or LiNTf2salt from the halide to IL-anion exchange.
- Rutz, Christina,Schmolke, Laura,Gvilava, Vasily,Janiak, Christoph
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supporting information
p. 130 - 135
(2017/02/05)
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- First observation for dynamic solvent effect in ionic liquids
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We observed pressure effects on the rate of thermal fading of colored chromene 1 photochemically generated from 2 in ionic liquids. The reaction rates were retarded with increasing pressure in [C4-mim][CS], [bzl-mim][Tf2N], and [mnp-mim][Tf2N], whereas the reaction rate increased with pressures in [C4- mim][Tf2N]. These pressure-induced retardations, so-called dynamic solvent effects, result from the slow thermal fluctuations of solvents.
- Kitaoka, Satoshi,Nobuoka, Kaoru,Miura, Junji,Ohga, Yasushi,Ishikawa, Yuichi
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p. 385 - 387
(2016/05/09)
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- Liquid-Crystalline Ionic Liquids as Ordered Reaction Media for the Diels–Alder Reaction
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Liquid-crystalline ionic liquids (LCILs) are ordered materials that have untapped potential to be used as reaction media for synthetic chemistry. This paper investigates the potential for the ordered structures of LCILs to influence the stereochemical outcome of the Diels–Alder reaction between cyclopentadiene and methyl acrylate. The ratio of endo- to exo-product from this reaction was monitored for a range of ionic liquids (ILs) and LCILs. Comparison of the endo:exo ratios in these reactions as a function of cation, anion and liquid crystallinity of the reaction media, allowed for the effects of liquid crystallinity to be distinguished from anion effects or cation alkyl chain length effects. These data strongly suggest that the proportion of exo-product increases as the reaction media is changed from an isotropic IL to a LCIL. A detailed molecular dynamics (MD) study suggests that this effect is related to different hydrogen bonding interactions between the reaction media and the exo- and endo-transition states in solvents with layered, smectic ordering compared to those that are isotropic.
- Bruce, Duncan W.,Gao, Yanan,Canongia Lopes, José Nuno,Shimizu, Karina,Slattery, John M.
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p. 16113 - 16123
(2016/10/26)
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- Surface tension of binary mixtures of 1-alkyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with alcohols
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New experimental surface tension data have been provided at 283.15, 298.15, 313.15 K and atmospheric pressure for binary mixtures of 1-butyl-3-methyl- imidazolium bis(trifluoromethylsulfonyl)imide and 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with the alcohols: methanol, ethanol, 1-propanol, 2-propanol, l-butanol and 1-pentanol. The experimental results show that the surface tensions of these mixtures depend systematically on the alkyl chain length of the ionic liquid and alcohol, composition and temperature. Surface tension changes on mixing have been calculated and adequately fitted by the Redlich-Kister polynomial equation. The adjustable parameters and the standard deviations between experimental and calculated values are reported.
- Andreatta, Alfonsina E.,Rodil, Eva,Arce, Alberto,Soto, Ana
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p. 404 - 420
(2014/03/21)
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- H2O2/NaHCO3-mediated enantioselective epoxidation of olefins in NTf2-based ionic liquids and under ultrasound
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The bicarbonate-activated peroxide (BAP) system has been shown to constitute an excellent and versatile combination for the epoxidation of olefins. Herein, we demonstrate that the benign H2O 2/NaHCO3 oxidative combination can be used for the enantioselective epoxidation of olefins using a chiral manganese porphyrin as a catalyst. This unprecedented result was made possible by the use of an ionic liquid with ultrasound, which leads to the activation of Mn-porphyrin catalysis.
- Chatel, Gregory,Goux-Henry, Catherine,Mirabaud, Anais,Rossi, Thomas,Kardos, Nathalie,Andrioletti, Bruno,Draye, Micheline
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p. 127 - 132
(2012/08/13)
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- Pseudo-encapsulation-nanodomains for enhanced reactivity in ionic liquids
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Domain constrained: Polar and nonpolar domains within 1-alkyl-3- methylimidazolium ionic liquids can affect reaction outcomes by pseudo-encapsulation of reactants and this has been explored for a nucleophilic substitution reaction using a cationic substrate and a range of nucleophiles. The significant rate enhancements observed correlate with the concentration of the polar reactants within the ionic liquid's polar domain. ([C nMIM]=1-alkyl-3-methylimidazolium). Copyright
- Weber, Cameron C.,Masters, Anthony F.,Maschmeyer, Thomas
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p. 11483 - 11486
(2013/01/15)
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- Sonochemical synthesis of 0D, 1D, and 2D zinc oxide nanostructures in ionic liquids and their photocatalytic activity
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Ultrasound synthesis of zinc oxide from zinc acetate and sodium hydroxide in ionic liquids (ILs) is a fast, facile, and effective, yet highly morphology- and size-selective route to zinc oxide nanostructures of various dimensionalities. No additional organic solvents, water, surfactants, or templating agents are required. Depending on the synthetic conditions, the selective manufacturing of 0D, 1D, and 2D ZnO nanostructures is possible: Whereas the formation of rodlike structures is typically favored, ZnO nanoparticles can be obtained either under strongly basic conditions or by use of ILs with a long alkyl chain, such as 1-n-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cnmim][Tf2N]; n>8). A short ultrasound irradiation time favors the formation of ZnO nanosheets. Prolonged irradiation leads to the conversion of the ZnO nanosheets into nanorods. In contrast, ionothermal synthesis (conventional heating) does not allow for morphology tuning by variation of the IL or other synthesis conditions, as the longer reaction times required lead always to the formation of well-developed hexagonal nanocrystals with prismatic tips. The ZnO nanostructures synthesized by using ultrasound were efficient photocatalysts in the photodegradation of methyl orange. The photoactivity was observed to be as high as 95 % for ZnO nanoparticles obtained in [C10mim][Tf 2N].
- Alammar, Tarek,Mudring, Anja-Verena
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experimental part
p. 1796 - 1804
(2012/04/04)
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- Synthesis of imidazolium and pyridinium-based ionic liquids and application of 1-alkyl-3-methylimidazolium salts as pre-catalysts for the benzoin condensation using solvent-free and microwave activation
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An efficient one-pot procedure for the synthesis of ionic liquids based on nitrogen-containing heterocycles, imidazolium or pyridinium under 'green chemistry' conditions has been described. Imidazolium salts and DBU have been found to catalyze efficiently the benzoin condensation giving good yields within very short reaction time using solvent-free microwave activation conditions.
- Aupoix, Audrey,Pégot, Bruce,Vo-Thanh, Giang
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scheme or table
p. 1352 - 1356
(2010/04/02)
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- Preparation of second generation ionic liquids by efficient solvent-free alkylation of N-heterocycles with chloroalkanes
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Non-conventional techniques, such as microwave (MW) and power ultrasound (US) as well as combined MW/US irradiation, have been used to promote one-pot synthesis of second-generation ionic liquids (ILs), cutting down reaction times and improving yields. However, the use of chloroalkanes in the alkylation of N-heterocycles requires more drastic conditions if results are to match those obtained with more reactive alkyl halides. The present paper describes a series of MW- or MW/US-promoted IL preparations starting from chloroalkanes and classic heterocycles (1-methylimidazole, pyridine and 1-methylpyrrolidine). When reactions were carried out under conventional heating in an oil bath they required longer reaction times and gave poorer yields. 1H-NMR analysis and ion-exchange chromatography showed that the present solventless procedure afforded ILs of satisfactory purity. The observed high yields (usually 70-98% isolated), and short reaction times showed that a straightforward access to ILs can be also achieved with the use of alkyl chlorides, resulting in a considerable reduction of costs.
- Cravotto, Giancarlo,Gaudino, Emanuela Calcio,Boffa, Luisa,Leveque, Jean-Marc,Estager, Julien,Bonrath, Werner
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p. 149 - 156
(2008/09/17)
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- A rationalization of the solvent effect on the Diels-Alder reaction in ionic liquids using multiparameter linear solvation energy relationships
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The Diels-Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) having different hydrogen bond acceptor abilities has been carried out in several ionic liquids and molecular solvents in order to obtain information about the factors affecting reactivity and selectivity. The solvent effects on these reactions are examined using multiparameter linear solvation energy relationships. The collected data provide evidence that the solvent effects are a function of both the solvent and the solute. For a solvent effect to be seen, the solute must have a complimentary character; selectivities and rates are determined by the solvent hydrogen bond donation ability (α) in the reactions of acrolein and methyl acrylate, but not of acrylonitrile. The Royal Society of Chemistry 2008.
- Bini, Riccardo,Chiappe, Cinzia,Mestre, Veronica Llopsis,Pomelli, Christian Silvio,Welton, Thomas
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supporting information; experimental part
p. 2522 - 2529
(2009/02/02)
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- A speedy one-pot synthesis of second-generation ionic liquids under ultrasound and/or microwave irradiation
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The present work describes an efficient one-pot synthesis of second-generation ionic liquids (ILs), combining in one step the Menshutkin reaction and anion metathesis. Working in a closed vessel under microwaves, or better still under simultaneous ultrasound and/or microwave irradiation, in a few minutes a series of ILs with 1-methylimidazole or pyridine cores were obtained in high yields (80?97% isolated). Under conventional heating, ILs could not be prepared in one pot in acceptable times and yields, whereas our protocol, carried out with commercially available equipment, was highly effective and reproducible. Moreover, 1H NMR analysis and ion-exchange chromatography showed that the present solventless procedure afforded satisfyingly pure ILs. CSIRO 2007.
- Cravotto, Giancarlo,Boffa, Luisa,L'Eveque, Jean-Marc,Estager, Julien,Draye, Micheline,Bonrath, Werner
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p. 946 - 950
(2008/03/17)
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- An acidity scale of 1,3-dialkylimidazolium salts in dimethyl sulfoxide solution
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(Chemical Equation Presented) Equilibrium acidities of 16 1,3-dialkylimidazolium-type ionic liquid (IL) molecules (1-16) were systematically measured by the overlapping indicator method at 25°C in dimethyl sulfoxide (DMSO) solution. The pKa values were observed to range from 23.4 for IL 12 to 19.7 for IL 6 (Tables 1 and 2), responding mainly to structural variations on the cation moiety. Excellent agreement between the spectrophotometrically determined pKa and that derived from NMR titration for 1,3,4,5-tetramethylimidazolium bis(trifluoromethanesulfonyl)imide (12) and the close match of the obtained pK values with the reported data in literature provide credence to the acidity measurements of the present work. The substituent effects at the imidazolium ring and the effects of counterions on the acidities of ionic liquids are discussed.
- Chu, Yuan,Deng, Hui,Cheng, Jin-Pei
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p. 7790 - 7793
(2008/02/13)
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- The HF/BF3-catalysed reaction of substituted benzenes with carbon monoxide
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The HF/BF3-catalysed reactions of phenol and anisole as well as substituted benzenes with CO were investigated as possible routes to commercially important aldehydes. The results confirmed that HF and BF 3 are required in (at least) stoichiometric amounts for effective formylation with CO. With the aim of effecting truly catalytic reaction conditions, the formylation reactions were carried out in ionic liquids. It was shown that phenol is a good substrate for formylation in certain ionic liquids. Georg Thieme Verlag Stuttgart.
- Willemse, J. Alexander,Bezuidenhoudt, Barend C. B.,Holzapfel, Cedric W.
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p. 2543 - 2550
(2008/02/04)
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- Determination of thermal diffusivities, thermal conductivities, and sound speeds of room-temperature ionic liquids by the transient grating technique
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We report measurements of thermal diffusivity of several room-temperature ionic liquids (RTILs) using the transient grating method. Measurements are carried out using ionic liquids with small concentrations of an inert dye that is excited by the 532 nm output of a Nd:YAG laser in a grating with a fringe spacings of (92 and 104) μm. The experiments give thermal diffusivities from which thermal conductivities can be determined, sound speeds, and acoustic damping parameters for seven ionic liquids. In this study, we have used combinations of the cation 1-butyl-3-methylimidazolium ([BMIm]+) with the anions tetrafluoroborate ([BF4]-), hexafluorophosphate ([PF6]-), and bis(trifluoromethylsulfonyl)imide ([Tf2N]-) and combinations of the anion [Tf2N]- with the cations 1-ethyl-3-methylimidazolium ([EMIm]+), 1-pentyl-3-methylimidazolium ([PMIm]+), 1-hexyl-3-methylimidazolium ([HMIm]+), and 1-octyl-3-methylimidazolium ([OMIm]+) to determine the effect of anion and cation on the thermophysical properties of the RTILs. Results obtained indicate that the anion exerts a strong influence not only on the sound speed but also on the thermal diffusivity and acoustic damping of the RTILs. For RTILs with the same cation [BMIm]+, changing the anion from [BF 4]- to either [PF6]- or [Tf 2N]- leads to decreases in the sound speed, thermal diffusivity, and thermal conductivity. The size of the cation, however, does not significantly influence the sound speed or the thermal diffusivity of the RTILs.
- Frez, Clifford,Diebold, Gerald J.,Tran, Chieu D.,Yu, Shaofang
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p. 1250 - 1255
(2007/10/03)
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- High-pressure phase behavior of carbon dioxide with imidazolium-based ionic liquids
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Previously we have shown that supercritical carbon dioxide can be used to extract organics from ionic liquids (ILs). Subsequently, ionic liquids/carbon dioxide biphasic solutions have been used for a variety of homogeneously catalyzed reactions. Therefore, an understanding of the phase behavior of carbon dioxide with ionic liquids is needed to design extraction and reaction processes necessary for these applications. We present measurements of the solubility of carbon dioxide in 10 different imidazolium-based ionic liquids at 25, 40, and 60?°C and pressures to 150 bar. As expected, the solubility increases with increasing pressure and decreases with increasing temperature for all the ILs investigated. To investigate the influence of the anion, seven of the ILs studied have 1-butyl-3-methylimidazolium ([bmim]) as the cation. The anions are dicyanamide ([DCA]), nitrate ([NO3]), tetrafluoroborate ([BF4]), hexafluorophosphate ([PF6]), trifuoromethanesulfonate ([TfO]), bis(trifluoromethylsulfonyl)imide ([Tf 2N]), and tris(trifluoromethylsulfonyl)methide ([methide]). The other ILs considered in the study, chosen to investigate the influence of varying number and length of alkyl chains on the cation, include 1-hexyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf2N]), 2,3-dimethyl-1-hexylimidazolium bis(trifluoromethylsulfonyl)imide ([hmmim][Tf2N]), and 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([omim][Tf2N]). Results show that the solubility of carbon dioxide is strongly dependent on the choice of anion. In particular, CO2 solubility is greater in ILs with anions, such as [Tf2N] and [methide], which contain fluoroalkyl groups. Also, we observe that an increase in the alkyl chain length on the cation increases the CO2 solubility marginally.
- Aki, Sudhir N. V. K.,Mellein, Berlyn R.,Saurer, Eric M.,Brennecke, Joan F.
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p. 20355 - 20365
(2008/01/27)
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- Solvent extraction of Sr2+ and Cs+ based on room-temperature ionic liquids containing monoaza-substituted crown ethers
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A series of N-alkyl aza-18-crown-6 ethers were synthesized and characterized by NMR spectroscopy and mass spectrometry. These monoaza-substituted crown ethers in ionic liquids were investigated as recyclable extractants for separation of Sr2+ and Cs+ from aqueous solutions. The pH-sensitive complexation capability of these ligands allows for a facile stripping process to be developed so that both macrocyclic ligands and ionic liquids can be reused. The extraction efficiencies and selectivities of these monoaza-substituted crown ethers for Na+, K+, Cs+, and Sr2+ were studied in comparison to those of dicyclohexano-18-crown-6 under the same conditions. The extraction selectivity order for dicyclohexano-18-crown-6 in the ionic liquids investigated here was K+ ? Sr2+ > Cs + > Na+. The extraction selectivity order for N-alkyl aza-18-crown-6, in which the alkyl group is varied systematically from ethyl to n-dodecyl, was Sr2+ ? K+ > Cs+ > Na+ in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and 1-butyl-3-methylimidazolium bis[(trifiuoromethyl)suffonyl]amide and K+ > Sr2+ > Cs+ > Na+ in 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide and 1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide. The strong dependence of selectivity on the type of ionic liquid indicates an important role played by solvation in solvent extraction processes based on ionic liquids. The optimization of macrocyclic ligands and ionic liquids led to an extraction system that is highly selective toward Sr2+.
- Luo, Huimin,Dai, Sheng,Bonnesen, Peter V.
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p. 2773 - 2779
(2007/10/03)
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