Showing papers on "Ionic liquid published in 1999"
12,178 citations
TL;DR: In this article, the authors showed that non-volatile organic compounds can be extracted from ionic liquids using supercritical carbon dioxide, which is widely used to extract large organic compounds with minimal pollution.
Abstract: Many organic solvents evaporate into the atmosphere with detrimental effects on the environment and human health. But room-temperature ionic liquids, with low viscosity and no measurable vapour pressure1, can be used as environmentally benign media for a range of industrially important chemical processes2,3,4,5,6, despite uncertainties about thermal stability and sensitivity to oxygen and water. It is difficult to recover products, however, as extraction with water7 works only for hydrophilic products, distillation is not suitable for poorly volatile or thermally labile products, and liquid-liquid extraction using organic solvents results in cross-contamination. We find that non-volatile organic compounds can be extracted from ionic liquids using supercritical carbon dioxide, which is widely used to extract large organic compounds with minimal pollution8. Carbon dioxide dissolves in the liquid to facilitate extraction, but the ionic liquid does not dissolve in carbon dioxide, so pure product can be recovered.
1,748 citations
TL;DR: In this article, 1-alkyl-3-methylimidazolium tetrafluoroborate (TFLB) is described as an isotropic ionic liquid with an enantiotropic smectic A mesophase.
Abstract: Air- and water-stable 1-alkyl-3-methylimidazolium tetrafluoroborate salts with the general formula [Cn-mim][BF4] (n = 0–18) have been prepared by metathesis from the corresponding chloride or bromide salts. The salts have been characterised by 1H NMR and IR spectroscopy, microanalysis, polarising optical microscopy and differential scanning calorimetry. Those with short alkyl chains (n = 2–10) are isotropic ionic liquids at room temperature and exhibit a wide liquid range, whereas the longer chain analogues are low melting mesomorphic crystalline solids which display an enantiotropic smectic A mesophase. The thermal range of the mesophase increases with increasing chain length and in the case of the longest chain salt prepared, [C18-mim][BF4], the mesophase range is ca. 150 °C.
1,169 citations
TL;DR: In this paper, the specific ionic conductivity, dynamic viscosity, and electrochemical stability of several imidazolium salts are reported as neationic liquids and their solutions in several organic solvents.
Abstract: The specific ionic conductivity, dynamic viscosity, and electrochemical stability of several imidazolium salts are reported as neationic liquids and their solutions in several organic solvents. The temperature dependence of conductivity and viscosity are analyzed for 1‐ethyl‐3‐methylimidazolium and 1,2‐dimethyl‐3‐n‐propylimidazolium salts, and the influence of theanions bis(trifluoromethylsulfonyl)imide , bis(perfluoroethylsulfonyl)imide , hexafluoroarsenate , hexafluorophosphate , and tetrafluoroborate on these properties are discussed. These imidazolium salts make possible electrolytes with high concentration (>3 M), high room temperature conductivity (up to 60 mS/cm), and a wide window of stability . Differential scanning calorimetric results confirm a large glass phase for the ionic liquids, with substantial (>80°C) supercooling. Thermal gravimetric results indicate the imidazolium salts with and anions to be thermally more stable than the lithium salt analogs. The Vogel‐Tammann‐Fulcher interpretation accurately describes the conductivity temperature dependence. © 1999 The Electrochemical Society. All rights reserved.
810 citations
TL;DR: In this paper, the authors show that unprecedented large distribution coefficient (D) values can be achieved using ionic liquids as extraction solvents for the separation of metal ions by crown ethers.
Abstract: The preliminary results described here show that unprecedentedly large distribution coefficient (D) values can be achieved using ionic liquids as extraction solvents for the separation of metal ions by crown ethers. This work highlights the vast opportunities in separation applications for ionic liquids with crown ethers.
650 citations
TL;DR: The Rohrschneider-McReynolds constants were determined for both ionic liquids and a popular commercial polysiloxane stationary phase, and it appears that the unusual properties of ions could make them beneficial in many areas of separation science.
Abstract: Stable room-temperature ionic liquids (RTILs) have been used as novel reaction solvents. They can solubilize complex polar molecules such as cyclodextrins and glycopeptides. Their wetting ability and viscosity allow them to be coated onto fused silica capillaries. Thus, 1-butyl-3-methylimidazolium hexafluorophosphate and the analogous chloride salt can be used as stationary phases for gas chromatography (GC). Using inverse GC, one can examine the nature of these ionic liquids via their interactions with a variety of compounds. The Rohrschneider-McReynolds constants were determined for both ionic liquids and a popular commercial polysiloxane stationary phase. Ionic liquid stationary phases seem to have a dual nature. They appear to act as a low-polarity stationary phase to nonpolar compounds. However, molecules with strong proton donor groups, in particular, are tenaciously retained. The nature of the anion can have a significant effect on both the solubilizing ability and the selectivity of ionic liquid s...
594 citations
TL;DR: Diels-Alder reactions in neutral ionic liquids (such as 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1- butyl- 3methyloride-imidazolate hexafluorophosphate) were reported in this paper, where rate enhancements and selectivities similar to those of reactions performed in lithium perchlorate-diethyl ether mixtures were observed.
452 citations
TL;DR: In this paper, aryl halides or benzoic anhydride with alkenes can be performed with excellent yields in room-temperature ionic liquids, which provide a medium that dissolves the palladium catalyst and allows the product and byproducts to be easily separated.
408 citations
TL;DR: The Diels-Alder cycloaddition reaction between methyl acrylate and cyclopentadiene has been investigated in a number of air and moisture stable ionic liquids as discussed by the authors.
377 citations
TL;DR: In this paper, the use of nonaqueous ionic liquids (NAILs) as an alternative to traditional molecular solvents for the Heck reaction has been shown to result in easy product separation, possible catalyst recycling and further increases in catalyst productivity.
200 citations
TL;DR: In this paper, the air and moisture stable system [bmim][BF4] and [Ru4(η6-C6H6)4] for hydrogenation of arenes is presented.
TL;DR: The utility of room temperature chloroaluminate ionic liquids as solvent and catalyst for the synthetically important Diels-Alder reaction was studied in this article, where the AlCl3-1-ethyl-3-methyl-1H-imidazolium chloride medium proved to be ideally suited for Diels Alder reactions.
TL;DR: In this paper, the authors reported the first measurements of the composition and molecular orientation at the surface of a room-temperature ionic liquid 1-butyl-3methylimidazolium hexafluorophosphate.
Abstract: We report the first measurements of the composition and molecular orientation at the surface of a room-temperature ionic liquid1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6]. Recoil spectrometry using rare gas ions on continuously refreshed liquid surfaces in vacuo shows that neither ion is significantly enriched in the surface. The average orientation of the cation is with the plane of the ring vertical. The cation ring is rotated about an axis through its center such that the nitrogen atoms and side chains are deeper in the surface with the surface normal passing between the two nitrogen atoms (with an estimated error of ±30°).
TL;DR: In this article, a two-phase technique using a homogeneous catalyst dissolved in water has been proposed, where the catalyst separation from the products can be easily achieved by simple phase decantation.
Abstract: One of the most important recent developments in homogeneous catalysis is the introduction of the aqueous two-phase technique. This method uses a homogeneous catalyst dissolved in water. The catalyst separation from the products can be easily achieved by simple phase decantation. Room-temperature ionic liquids based on organic cations, such as dialkylimidazolium, and inorganic anions, such as AlCl 4 - , Al 2 Cl 7 - , BF 4 - , PF 6 - and SbF 6 - , offer an extension to this field especially when substrates, organometallic complexes and ligands are poorly soluble or unstable in water. They present a large spectrum of physical and chemical properties which can be adjusted at will to a given catalytic organic reaction. Nickel catalyzed butene dimerization has been recently developed using chloroaluminate based ionic liquids as the solvent. Ionic liquids containing weakly coordinating anions such as BF 4 - , are good solvents for Diels-Alder reactions.
TL;DR: In this article, the reaction of 1-ethyl-3-methyl imidazolium chloride (EMIC) and hydrogen fluoride gives an yellow, involatile liquid, EMIF·2.3HF.
TL;DR: In this article, 4-and 5-methyl thiazole is readily alkylated with n-butyl bromide followed by anion exchange of Br− for BF4− to give mobile, room-temperature ionic liquids.
TL;DR: In this article, the use of buffered ionic liquid as a solvent for catalysts known to produce linear dimers from but-1-ene has been explored; this resulted in a significant enhancement of the activity of known catalysts, combined with the retention of both dimer selectivity and product linearity; in addition, the biphasic mode of operation allows easy catalyst recovery and recycle.
TL;DR: In this paper, the effect of varying the "bulk" Lewis acidity of the ionic liquids used as solvents in these reactions is also described, as well as varying the relative amounts of acylating agent with respect to the amount of ferrocene.
Abstract: Friedel–Crafts acylations of ferrocene in 1-ethyl-3-methylimidazolium halogenoaluminate ionic liquids, [emim]I–(AlCl3)x are described.3 The effect of varying the “bulk” Lewis acidity of the ionic liquids used as solvents in these reactions and the effect of varying the relative amounts of acylating agent with respect to the amount of ferrocene in these reactions is also described. The use of a variety of different acylating agents in our studies demonstrates the scope of this reaction performed in these ionic liquid systems.
TL;DR: Palladium catalysed allylic alkylation and amination reactions have been demonstrated to proceed readily in the room temperature ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([bmim][BF4]) with easy catalyst/solvent recycling and no need to generate separately the carbanion nucleophiles.
TL;DR: In this article, the Trost-Tsuji C-C coupling between ethyl cinnamyl carbonate and ethyl acetoacetate catalysed by a water soluble Pd/TPPTS catalyst (TPPTS=triphenylphosphine trisulphonate, sodium salt) was investigated in several biphasic media at 60-80°C.
Abstract: AbstractThe Trost–Tsuji C–C coupling between ethyl cinnamyl carbonate and ethyl acetoacetate catalysed by a water soluble Pd/TPPTS catalyst (TPPTS=triphenylphosphine trisulphonate, sodium salt) and possible side reactions have been investigated in several biphasic media at 60–80°C. The use of the ionic liquid 1-butyl-3-methylimidazolium chloride as the catalytic layer brings definitive advantages over an aqueous catalytic phase: Palladium chloride may be used as the catalyst precursor, the solubility of the organic reagents is much higher which leads to faster reaction rates, the formation of cinnamyl alcohol is suppressed and common organic layers such as alkanes can be used with no noticeable catalyst deactivation. The yields in the C–C product up to 90% with TOF numbers of 23 h−1 may, thus, be achieved.
TL;DR: Stereoselective hydrogenation reactions in the ionic liquid system 1-ethyl-3methylimidazolium chloride-AlCl3 can be performed with excellent yields and selectivities, using electropositive metals and a proton source.
Patent•
28 Jan 1999
TL;DR: A highly dispersed iron-based ionic liquid or liquid-gel catalyst which may be anion modified and metals-promoted has high catalytic activity, and is useful for hydrocracking/hydrogenation reactions for carbonaceous feed materials.
Abstract: A highly dispersed iron-based ionic liquid or liquid-gel catalyst which may be anion-modified and metals-promoted has high catalytic activity, and is useful for hydrocracking/hydrogenation reactions for carbonaceous feed materials. The catalyst is produced by aqueous precipitation from saturated iron salt solutions such as ferric sulfate and ferric alum, and may be modified during preparation with anionic sulfate (SO4 2-) and promoted with small percentages of at least one active metal such as cobalt, molybdenum, palladium, platinum, nickel, or tungsten or mixtures thereof. The resulting catalyst may be used in a preferred ionic liquid form or in a liquid-gel form, and either fluidic form can be easily mixed and reacted with carbonaceous feed materials such as coal, heavy petroleum fractions, mixed plastic waste, or mixtures thereof. The invention includes methods for making the ionic liquid or liquid-gel catalyst, and processes for using the fluidic catalysts for hydroprocessing the carbonaceous feed materials to produce desirable low-boiling hydrocarbon liquid products.
Patent•
03 Dec 1999TL;DR: Ionic liquids function as initiator or as a co-solvent for the production of very high molecular weight polyisobutylenes, e.g., having a weight-average molecular weight over 100,000.
Abstract: Ionic liquids function as the initiator or as a co-solvent for the production of very high molecular weight polyisobutylenes, e.g., having a weight-average molecular weight over 100,000. These ionic liquids may be characterized by the general formula A+B- where A+ represents any stable inorganic or organic cation and B- represents any stable organic or inorganic anion.
TL;DR: Ionic liquids based on the 1-butyl-3methylimidazolium cation have been used as solvents for the preparation in good yield of homoallylic alcohols from tetraallylstannane and a range of aldehydes as discussed by the authors.
Patent•
20 Dec 1999TL;DR: In this article, the authors present methods and apparatus for vaporizing and transporting precursor molecules to a process chamber for deposition of thin films on a substrate, using CVD solvents that comprise ionic liquids.
Abstract: The present invention provides methods and apparatus for vaporizing and transporting precursor molecules to a process chamber for deposition of thin films on a substrate. The methods and apparatus include CVD solvents that comprise ionic liquids. The ionic liquids comprise salt compounds that have substantially no measurable vapor pressure (i.e., less than about 1 Torr at about room temperature), exhibit a wide liquid temperature range (i.e., greater than about 100° C.), and have low melting points (i.e., less than about 250° C.). A desired precursor is dissolved in a selected CVD solvent comprising an ionic liquid. The solvent and precursor solution is heated to or near the precursor volatilization temperature of the precursor. A stream of carrier gas is directed over or is bubbled through the solvent and precursor solution to distill and transport precursor molecules in the vapor phase to a deposition chamber. Conventional deposition processes may be used to deposit the desired thin film on a substrate.
TL;DR: In this article, the two anions bis(trifluoromethylsulfonyl)imide (Im) and bis(perfluoroethylsulfonyl)imides (Beti) display similar passivation on aluminum in solvent-free ionic liquids.
Abstract: The two anions bis(trifluoromethylsulfonyl)imide (Im) and bis(perfluoroethylsulfonyl)imide (Beti) display similar passivation on aluminum in solvent-free ionic liquids. The addition of 10% propylene carbonate to the ionic liquids EMIIm and EMIBeti (EMI: 1-ethyl-3-methyl imidazolium) introduces oxidative corrosion, with the Beti anion being 0.7 V more stable. The oxidation peaks are shifted to more positive potentials (ca. 0.1 V) with the addition of the lithium salt. The results from cyclic voltammetry and chronoamperometric experiments indicate propylene carbonate to be an active participant in the corrosion process on aluminum. © 1999 The Electrochemical Society. S1099-0062(99)02-039-8. All rights reserved.
TL;DR: In this paper, an in situ method of studying the structure of reactive ionic materials in the solid and liquid states by XAFS is described, and the results show that their structure may be studied using transmission X-AFS by utilizing pressed disks of BN, graphite and LiF and is not affected by the sample matrix used.
Abstract: An in situ method of studying the structure of reactive ionic materials in the solid and liquid states by XAFS is described. These salts have novel catalytic and solvent properties, and the results show that their structure may be studied using transmission XAFS by utilizing pressed disks of BN, graphite, and LiF and is not affected by the sample matrix used.
Patent•
14 Oct 1999
TL;DR: In this article, an electrolyte for a lithium rechargeable cell is described which contains a pyrazolium cation and may also contain a lithium salt, such as LiBF 4, LiAsF 6, LiPF 6, and LiTF.
Abstract: An electrolyte, such as for a lithium rechargeable cell, is described which contains a pyrazolium cation and may also contain a lithium salt. The lithium salt may be at least one of LiBF 4 , LiAsF 6 , LiPF 6 , and LiTF. The electrolyte, when used in an electrochemical cell, has a charge/discharge capacity and charging efficiency that is superior to the same properties of ionic liquid electrolytes without a pyrazolium cation. Electrochemical cells are also described and contain an anode, a cathode, and the pyrazolium cation electrolyte.
TL;DR: In this paper, transition metal-cyclophane complexes using the ionic liquid system (i.e., Cl-AlCl 3 and 1-butyl-3methylimidazolium cation) as both the solvent and Lewis acid catalyst are described.