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Special Issue "Ionic Liquids"

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A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: closed (29 February 2012)

Special Issue Editor

Guest Editor
Dr. Werner Bonrath

DSM Nutritional Products, Research and Development, CH-4002 Basel, Switzerland
Fax: +41 61 687 21 17
Interests: catalysis (general); vitamins (general); chemistry under non-classical conditions (ionic liquids; supercritical fluids; ultrasound and microwaves)

Keywords

  • ionic liquids, molten salts
  • room temperature ionic liquids
  • low temperature ionic liquids
  • 1. -3. generation of ionic liquids
  • immidazolium salts
  • pyridinuim salts
  • Baylis-Hillmann reaction
  • Diels–Alder reactions.

Published Papers (25 papers)

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Research

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Open AccessArticle Effect of Ionic Liquid on the Determination of Aromatic Amines as Contaminants in Hair Dyes by Liquid Chromatography Coupled to Electrochemical Detection
Molecules 2012, 17(7), 7961-7979; doi:10.3390/molecules17077961
Received: 16 May 2012 / Revised: 24 June 2012 / Accepted: 25 June 2012 / Published: 2 July 2012
Cited by 9 | PDF Full-text (1022 KB)
Abstract
The room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis-(trifluorometanesulfonyl)imide BMIm[NTf2] was used as a novel medium for improvement of separation and quantization of 16 aromatic amines typically present as contaminants in consumer products and detected by HPLC coupled to an electrochemical [...] Read more.
The room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis-(trifluorometanesulfonyl)imide BMIm[NTf2] was used as a novel medium for improvement of separation and quantization of 16 aromatic amines typically present as contaminants in consumer products and detected by HPLC coupled to an electrochemical detector. The aromatic amines, namely 4,4'-diaminodiphenylmethane, 4-chloroaniline, 2-methoxy-5-methyl-aniline, 3,3'-dimethylbenzidine, 2,4-diaminotoluidine, 2-chloro-4-nitroaniline, 4,4'-oxydianiline, aniline, 3,3'-dichlorobenzidine, benzidine, 4-aminobiphenyl, o-dianisidine, o-anisidine, o-toluidine, 4,4'-methylene-bis-2-chloroaniline and 2-naphthyl-amine are oxidized in methanol/BMIm[NTf2] at a potential around +0.68V to +0.93V vs. Ag/AgCl at a glassy carbon electrode, which is the base for their determination by HPLC/ED. Using the optimized conditions of methanol/BMIm[NTf2] 70:30 (v/v) as mobile phase, flow-rate of 0.8 mL·min−1, column CLC-ODS, Eap = +1.0 V and T = 40 °C analytical curves were constructed for each of the tested amines. Good linearity was obtained in the concentration range of 1.09 mg·L−1 to 217 mg·L−1, with excellent correlation coefficients. The limits of detection reached 0.021 mg·L−1 to 0.246 mg·L−1 and good relative standard deviations (RSD, n = 3) were obtained from the measurements. Satisfactory recovery for each aromatic amine was achieved, ranging from 95 to 103%. The developed method was successfully applied to determine six aromatic amines present as contaminants in commercial hair dye samples. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle In Situ Electrochemical SFG/DFG Study of CN and Nitrile Adsorption at Au from 1-Butyl-1-methyl-pyrrolidinium Bis(trifluoromethylsulfonyl) Amide Ionic Liquid ([BMP][TFSA]) Containing 4-{2-[1-(2-Cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]diazenyl} Benzonitrile (CTDB) and K[Au(CN)2]
Molecules 2012, 17(7), 7722-7736; doi:10.3390/molecules17077722
Received: 21 March 2012 / Revised: 22 May 2012 / Accepted: 23 May 2012 / Published: 25 June 2012
Cited by 3 | PDF Full-text (638 KB)
Abstract
In this paper we report an in situ electrochemical Sum-/Difference Frequency Generation (SFG/DFG) spectroscopy investigation of the adsorption of nitrile and CN from the ionic liquid 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]) containing 4-{2-[1-(2-cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]- diazenyl}benzonitrile (CTDB) at Au electrodes in the absence and [...] Read more.
In this paper we report an in situ electrochemical Sum-/Difference Frequency Generation (SFG/DFG) spectroscopy investigation of the adsorption of nitrile and CN from the ionic liquid 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]) containing 4-{2-[1-(2-cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]- diazenyl}benzonitrile (CTDB) at Au electrodes in the absence and in the presence of the Au-electrodeposition process from K[Au(CN)2]. The adsorption of nitrile and its coadsorption with CN resulting either from the cathodic decomposition of the dye or from ligand release from the Au(I) cyanocomplex yield potential-dependent single or double SFG bands in the range 2,125–2,140 cm1, exhibiting Stark tuning values of ca. 3 and 1 cm1 V1 in the absence and presence of electrodeposition, respectively. The low Stark tuning found during electrodeposition correlates with the cathodic inhibiting effect of CTDB, giving rise to its levelling properties. The essential insensitivity of the other DFG parameters to the electrodeposition process is due to the growth of smooth Au. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle A Convenient Synthesis of Triflate Anion Ionic Liquids and Their Properties
Molecules 2012, 17(5), 5319-5338; doi:10.3390/molecules17055319
Received: 7 March 2012 / Revised: 13 April 2012 / Accepted: 13 April 2012 / Published: 7 May 2012
Cited by 13 | PDF Full-text (355 KB)
Abstract
A solvent- and halogen-free synthesis of high purity triflate ionic liquids via direct alkylation of organic bases (amines, phosphines or heterocyclic compounds) with methyl and ethyl trifluoromethanesulfonate (methyl and ethyl triflate) has been developed. Cheap and non-toxic dimethyl and diethyl carbonate serve [...] Read more.
A solvent- and halogen-free synthesis of high purity triflate ionic liquids via direct alkylation of organic bases (amines, phosphines or heterocyclic compounds) with methyl and ethyl trifluoromethanesulfonate (methyl and ethyl triflate) has been developed. Cheap and non-toxic dimethyl and diethyl carbonate serve as source for the methyl and ethyl groups in the preparation of methyl and ethyl triflate by this invented process. The properties of ionic liquids containing the triflate anion are determined and discussed. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle Preparation of SRN1-Type Coupling Adducts from Aliphatic gem-Dinitro Compounds in Ionic Liquids
Molecules 2012, 17(5), 4782-4790; doi:10.3390/molecules17054782
Received: 29 February 2012 / Revised: 2 April 2012 / Accepted: 12 April 2012 / Published: 25 April 2012
PDF Full-text (212 KB) | Supplementary Files
Abstract
SRN1-type coupling adducts are readily prepared by the reaction between a-sulfonylesters or a-cyanosulfones and gem-dinitro compounds in ionic liquids. The reactions progress smoothly and recovered ionic liquids can be used for several iterations, as long as they are washed [...] Read more.
SRN1-type coupling adducts are readily prepared by the reaction between a-sulfonylesters or a-cyanosulfones and gem-dinitro compounds in ionic liquids. The reactions progress smoothly and recovered ionic liquids can be used for several iterations, as long as they are washed with water to remove alkali metallic salts. The reaction rate is slower than the corresponding SRN1 reaction in DMSO, but no acceleration on irradiation or no inhibition in the presence of m-DNB are observed. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle A Simple Halide-to-Anion Exchange Method for Heteroaromatic Salts and Ionic Liquids
Molecules 2012, 17(4), 4007-4027; doi:10.3390/molecules17044007
Received: 29 February 2012 / Revised: 20 March 2012 / Accepted: 23 March 2012 / Published: 2 April 2012
Cited by 7 | PDF Full-text (472 KB) | HTML Full-text | XML Full-text
Abstract
A broad and simple method permitted halide ions in quaternary heteroaromatic and ammonium salts to be exchanged for a variety of anions using an anion exchange resin (A form) in non-aqueous media. The anion loading of the AER (OH form) [...] Read more.
A broad and simple method permitted halide ions in quaternary heteroaromatic and ammonium salts to be exchanged for a variety of anions using an anion exchange resin (A form) in non-aqueous media. The anion loading of the AER (OH form) was examined using two different anion sources, acids or ammonium salts, and changing the polarity of the solvents. The AER (A form) method in organic solvents was then applied to several quaternary heteroaromatic salts and ILs, and the anion exchange proceeded in excellent to quantitative yields, concomitantly removing halide impurities. Relying on the hydrophobicity of the targeted ion pair for the counteranion swap, organic solvents with variable polarity were used, such as CH3OH, CH3CN and the dipolar nonhydroxylic solvent mixture CH3CN:CH2Cl2 (3:7) and the anion exchange was equally successful with both lipophilic cations and anions. Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessArticle Coupling of Nanoporous Chromium, Aluminium-Containing Silicates with an Ionic Liquid for the Transformation of Glucose into 5-(Hydroxymethyl)-2-furaldehyde
Molecules 2012, 17(4), 3690-3707; doi:10.3390/molecules17043690
Received: 17 February 2012 / Revised: 6 March 2012 / Accepted: 20 March 2012 / Published: 26 March 2012
Cited by 4 | PDF Full-text (746 KB) | HTML Full-text | XML Full-text
Abstract
Micro/mesoporous chromium, aluminium-containing silicates of the type TUD-1 (Al-TUD-1, Cr-TUD-1, CrAl-TUD-1) and zeolite BEA, Cr-BEA, and related composites BEA/TUD-1 and Cr-BEA/TUD-1, were prepared, characterised, and tested as solid acids coupled with the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([bmim]Cl) as solvent, in the [...] Read more.
Micro/mesoporous chromium, aluminium-containing silicates of the type TUD-1 (Al-TUD-1, Cr-TUD-1, CrAl-TUD-1) and zeolite BEA, Cr-BEA, and related composites BEA/TUD-1 and Cr-BEA/TUD-1, were prepared, characterised, and tested as solid acids coupled with the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([bmim]Cl) as solvent, in the transformation of d-glucose into 5-(hydroxymethyl)-2-furaldehyde (Hmf), at 120 °C. The chromium-containing catalytic systems lead to considerably higher Hmf yields in comparison to the related systems without chromium. The IL is a favourable solvent for this target reaction (in terms of Hmf yields reached) compared to water or dimethylsulfoxide. A detailed study on the stabilities of the nanoporous solid acids in the IL medium is presented. Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessCommunication The Solubility of Hen Lysozyme in Ethylammonium Nitrate/H2O Mixtures and a Novel Approach to Protein Crystallization
Molecules 2010, 15(2), 793-803; doi:10.3390/molecules15020793
Received: 16 December 2009 / Revised: 2 February 2010 / Accepted: 4 February 2010 / Published: 4 February 2010
Cited by 19 | PDF Full-text (206 KB)
Abstract
We report on the solubility of hen lysozyme (HEWL) in aqueous ethylammonium nitrate (EAN) as a function of water content. We find the solubility behavior to be complex, exhibiting both a maximum (400 mg/mL) at very high EAN content) and a minimum [...] Read more.
We report on the solubility of hen lysozyme (HEWL) in aqueous ethylammonium nitrate (EAN) as a function of water content. We find the solubility behavior to be complex, exhibiting both a maximum (400 mg/mL) at very high EAN content) and a minimum at intermediate EAN content. We exploit this solubility profile in a novel approach to generating crystals of hydrophilic proteins, based on rehydration of a high concentration protein solution. We describe the production of crystals of X-ray diffraction quality. Two related ionic liquid solvent systems, with the same solubility profiles but different effective pH characteristics, are identified for future evaluation. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle 18-Crown-6 and Dibenzo-18-crown-6 Assisted Extraction of Cesium from Water into Room Temperature Ionic Liquids and Its Correlation with Stability Constants for Cesium Complexes
Molecules 2009, 14(12), 5001-5016; doi:10.3390/molecules14125001
Received: 1 September 2009 / Revised: 24 November 2009 / Accepted: 27 November 2009 / Published: 2 December 2009
Cited by 17 | PDF Full-text (278 KB)
Abstract
The pH-profiles of the extraction of Cs+ into four conventional (1-butyl-3-methylimidazolium hexafluorophosphate and bis[trifluoromethyl)sulphonyl]imides of 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, and 1-(2-ethylhexyl)-3- methylimidazolium) and two novel (trioctylmethylammonium salicylate and tetrahexylammonium dihexylsulfosuccinate) room temperature ionic liquids have been determined both in the absence and in [...] Read more.
The pH-profiles of the extraction of Cs+ into four conventional (1-butyl-3-methylimidazolium hexafluorophosphate and bis[trifluoromethyl)sulphonyl]imides of 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, and 1-(2-ethylhexyl)-3- methylimidazolium) and two novel (trioctylmethylammonium salicylate and tetrahexylammonium dihexylsulfosuccinate) room temperature ionic liquids have been determined both in the absence and in the presence of crown ether (18-crown-6 or dibenzo-18-crown-6). The pH-profiles of distribution ratio of crown ethers have been established in the same conditions. The relationship of cesium extraction efficiency both with the stability of its complexes with crown ethers and crown ethers’ distribution ratio has been clarified. Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessArticle Cellulose/Gold Nanocrystal Hybrids via an Ionic Liquid/Aqueous Precipitation Route
Molecules 2009, 14(11), 4682-4688; doi:10.3390/molecules14114682
Received: 9 October 2009 / Revised: 12 November 2009 / Accepted: 17 November 2009 / Published: 18 November 2009
Cited by 11 | PDF Full-text (764 KB)
Abstract
Injection of a mixture of HAuCl4 and cellulose dissolved in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride [Bmim]Cl into aqueous NaBH4 leads to colloidal gold nanoparticle/cellulose hybrid precipitates. This process is a model example for a very simple and generic approach towards [...] Read more.
Injection of a mixture of HAuCl4 and cellulose dissolved in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride [Bmim]Cl into aqueous NaBH4 leads to colloidal gold nanoparticle/cellulose hybrid precipitates. This process is a model example for a very simple and generic approach towards (noble) metal/cellulose hybrids, which could find applications in sensing, sterile filtration, or as biomaterials. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle 1-Methyl-3-octylimidazolium Chloride—Sorption and Primary Biodegradation Analysis in Activated Sewage Sludge
Molecules 2009, 14(11), 4396-4405; doi:10.3390/molecules14114396
Received: 30 August 2009 / Revised: 28 October 2009 / Accepted: 30 October 2009 / Published: 2 November 2009
Cited by 18 | PDF Full-text (158 KB)
Abstract
Ionic liquids (ILs) are known to be non-volatile and thus to have low potential for atmospheric contamination or intoxication of humans by inhalation. However ILs have the potential to contaminate soil and water as they might be water soluble and can be [...] Read more.
Ionic liquids (ILs) are known to be non-volatile and thus to have low potential for atmospheric contamination or intoxication of humans by inhalation. However ILs have the potential to contaminate soil and water as they might be water soluble and can be sorbed onto solids. The investigation of possible natural ways of reducing the concentration of ILs in the environment is of high importane, especially because the requirement for biodegradable chemicals increases, together with pressure for reduction of incineration and landfill waste. It was found that the upper concentration threshold for primary biodegradation of 1-methyl-3-octylimidazolium chloride is 0.2 mM. At higher concentrations the dehydrogenase activity of the cells dropped markedly, indicating that the IL inhibits cell activity. This concentration is in good agreement with the minimal inhibitory concentration of the same compound found for a series of bacteria and fungi by this research group. The sorption of 1-methyl-3-octylimidazolium chloride was found to be significant, and the sorption coefficient was determined to be 98.2 L kg-1. Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessArticle Oxidative Desulfurization of Fuel Oil by Pyridinium-Based Ionic Liquids
Molecules 2009, 14(11), 4351-4357; doi:10.3390/molecules14114351
Received: 9 September 2009 / Revised: 8 October 2009 / Accepted: 19 October 2009 / Published: 28 October 2009
Cited by 31 | PDF Full-text (93 KB)
Abstract
In this work, an N-butyl-pyridinium-based ionic liquid [BPy]BF4 was prepared. The effect of extraction desulfurization on model oil with thiophene and dibenzothiophene (DBT) was investigated. Ionic liquids and hydrogen peroxide (30%) were tested in extraction-oxidation desulfurization of model oil. The [...] Read more.
In this work, an N-butyl-pyridinium-based ionic liquid [BPy]BF4 was prepared. The effect of extraction desulfurization on model oil with thiophene and dibenzothiophene (DBT) was investigated. Ionic liquids and hydrogen peroxide (30%) were tested in extraction-oxidation desulfurization of model oil. The results show that the ionic liquid [BPy]BF4 has a better desulfurization effect. The best technological conditions are: V(IL)/V(Oil) /V(H2O2) = 1:1:0.4, temperature 55 °C, the time 30 min. The ratio of desulfurization to thiophene and DBT reached 78.5% and 84.3% respectively, which is much higher than extraction desulfurization with simple ionic liquids. Under these conditions, the effect of desulfurization on gasoline was also investigated. The used ionic liquids can be recycled up to four times after regeneration. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessCommunication Preparation of (S)-1-Halo-2-octanols Using Ionic Liquids and Biocatalysts
Molecules 2009, 14(10), 4275-4283; doi:10.3390/molecules14104275
Received: 31 August 2009 / Revised: 26 September 2009 / Accepted: 16 October 2009 / Published: 23 October 2009
Cited by 5 | PDF Full-text (192 KB)
Abstract
Preparation of (S)-1-chloro-2-octanol and (S)-1-bromo-2-octanol was carried out by the enzymatic hydrolysis of halohydrin palmitates using biocatalysts. Halohydrin palmitates were prepared by various methods from palmitic acid and 1,2-octanediol. A tandem hydrolysis was carried out using lipases from [...] Read more.
Preparation of (S)-1-chloro-2-octanol and (S)-1-bromo-2-octanol was carried out by the enzymatic hydrolysis of halohydrin palmitates using biocatalysts. Halohydrin palmitates were prepared by various methods from palmitic acid and 1,2-octanediol. A tandem hydrolysis was carried out using lipases from Candida antarctica (Novozym® 435), Rhizomucor miehei (Lipozyme IM), and “resting cells” from a Rhizopus oryzae strain that was not mycotoxigenic. The influence of the enzyme and the reaction medium on the selective hydrolysis of isomeric mixtures of halohydrin esters is described. Novozym® 435 allowed preparation of (S)-1-chloro-2-octanol and (S)-1-bromo-2-octanol after 1–3 h of reaction at 40 °C in [BMIM][PF6]. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle Catalytic Epoxidation of a Technical Mixture of Methyl Oleate and Methyl Linoleate in Ionic Liquids Using MoO(O2)2•2QOH (QOH = 8-quinilinol) as Catalyst and NaHCO3 as co-Catalyst
Molecules 2009, 14(8), 2935-2946; doi:10.3390/molecules14082935
Received: 2 July 2009 / Revised: 3 August 2009 / Accepted: 5 August 2009 / Published: 10 August 2009
Cited by 19 | PDF Full-text (271 KB) | HTML Full-text | XML Full-text
Abstract
The oxo-diperoxo molybdenum(VI) complex MoO(O2)2•2QOH (QOH = 8-quinilinol) was prepared and characterized by elemental analysis, IR and UV-Vis spectra. The ionic liquids (ILs) [bmim][BF4], [hydemim][BF4], and [bmim][PF6] were characterized by 1H-NMR [...] Read more.
The oxo-diperoxo molybdenum(VI) complex MoO(O2)2•2QOH (QOH = 8-quinilinol) was prepared and characterized by elemental analysis, IR and UV-Vis spectra. The ionic liquids (ILs) [bmim][BF4], [hydemim][BF4], and [bmim][PF6] were characterized by 1H-NMR and UV-Vis spectra. The epoxidation of a technical mixture of methyl oleate and methyl linoleate with H2O2, in [bmim][BF4], [hydemim][BF4] and [bmim][PF6], catalyzed by MoO(O2)2•2QOH (QOH = 8-quinilinol) and with NaHCO3 as co-catalyst has been studied for the first time. It was found that high conversions of methyl oleate and methyl linoleate to their respective oxidation products, as well as the total selectivity of their oxidation products to oxirane in [hydemim][BF4] were obtained. Also, the IL phases containing the Mo(VI) catalyst can be readily recycled by washing with diethyl ether and drying, and the Mo(VI) catalyst can be reused at least five times. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle Ionic Liquids: Just Molten Salts After All?
Molecules 2009, 14(7), 2521-2534; doi:10.3390/molecules14072521
Received: 7 June 2009 / Revised: 6 July 2009 / Accepted: 10 July 2009 / Published: 13 July 2009
Cited by 31 | PDF Full-text (348 KB) | HTML Full-text | XML Full-text
Abstract
While there has been much effort in recent years to characterise ionic liquids in terms of parameters that are well described for molecular solvents, using these to explain reaction outcomes remains problematic. Herein we propose that many reaction outcomes in ionic liquids [...] Read more.
While there has been much effort in recent years to characterise ionic liquids in terms of parameters that are well described for molecular solvents, using these to explain reaction outcomes remains problematic. Herein we propose that many reaction outcomes in ionic liquids may be explained by considering the electrostatic interactions present in the solution; that is, by recognising that ionic liquids are salts. This is supported by evidence in the literature, along with studies presented here. Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessArticle Transformations of Organic Molecules with F-TEDA-BF4 in Ionic Liquid Media
Molecules 2009, 14(7), 2394-2409; doi:10.3390/molecules14072394
Received: 11 May 2009 / Revised: 10 June 2009 / Accepted: 3 July 2009 / Published: 6 July 2009
Cited by 10 | PDF Full-text (217 KB) | HTML Full-text | XML Full-text
Abstract
The transformations of organic molecules with F-TEDA-BF4 (1) were investigated in the hydrophilic ionic liquid (IL) 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF4], 2) and the hydrophobic IL 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF6], 3). The range of substrates included alkyl substituted phenols 4a-c, [...] Read more.
The transformations of organic molecules with F-TEDA-BF4 (1) were investigated in the hydrophilic ionic liquid (IL) 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF4], 2) and the hydrophobic IL 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF6], 3). The range of substrates included alkyl substituted phenols 4a-c, 9, 13, 1,1-diphenylethene (15), alkyl aryl ketones 19-22, aldehydes 23-25 and methoxy-substituted benzene derivatives 26-30. The evaluation of the outcome of reactions performed in IL media in comparison to those of the corresponding reactions in conventional organic solvents revealed that the transformations in IL are less efficient and selective. The effect of the presence of a nucleophile (MeOH, H2O, MeCN) on the course of reaction was also studied. Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessArticle A Facile Route to C2-Substituted Imidazolium Ionic Liquids
Molecules 2009, 14(6), 2235-2245; doi:10.3390/molecules14062235
Received: 14 May 2009 / Revised: 10 June 2009 / Accepted: 16 June 2009 / Published: 19 June 2009
Cited by 15 | PDF Full-text (206 KB)
Abstract
A convenient route for the preparation of C2-substituted imidazolium ionic liquids is reported. This method involves the alkylation of N-heterocyclic carbenes, which are readily generated from the C2-unsubstituted imidazolium ionic liquids. It works well for non-functionalized alkyl chlorides, and less well [...] Read more.
A convenient route for the preparation of C2-substituted imidazolium ionic liquids is reported. This method involves the alkylation of N-heterocyclic carbenes, which are readily generated from the C2-unsubstituted imidazolium ionic liquids. It works well for non-functionalized alkyl chlorides, and less well for alkyl bromides and iodides, likely due to competing elimination reactions. The resulting C2-substituted salts can be transformed into ionic liquids via standard anion metathesis reactions. Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessArticle Effect of Ionic Liquids as the Mobile Phase Additives on the HPLC Resolution of Four Active Compounds from Sophora flavescens Ait
Molecules 2009, 14(6), 2127-2134; doi:10.3390/molecules14062127
Received: 17 April 2009 / Revised: 7 May 2009 / Accepted: 2 June 2009 / Published: 11 June 2009
Cited by 12 | PDF Full-text (120 KB) | HTML Full-text | XML Full-text
Abstract
The retention behaviour of four active compounds from Sophora Flavescens Ait using three ionic liquids as mobile phase modifiers was examined. The effect of the pH and the amount of ionic liquid modifier on the retention of these compounds was determined in [...] Read more.
The retention behaviour of four active compounds from Sophora Flavescens Ait using three ionic liquids as mobile phase modifiers was examined. The effect of the pH and the amount of ionic liquid modifier on the retention of these compounds was determined in methanol/water (v/v) as the mobile phase containing different ionic liquids ranging in concentration from 0.1 mmol/L to 3.0 mmol/L. The ionic liquids showed promise as additives in high-performance liquid chromatography. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessArticle Synthesis and Properties of Acyclic Ammonium-based Ionic Liquids with Allyl Substituents as Electrolytes
Molecules 2009, 14(5), 1840-1851; doi:10.3390/molecules14051840
Received: 18 April 2009 / Revised: 12 May 2009 / Accepted: 13 May 2009 / Published: 15 May 2009
Cited by 10 | PDF Full-text (177 KB)
Abstract
Several new acyclic ammonium-TFSI ionic liquids with an allyl substituent(s) were synthesized and their physicochemical and electrochemical properties were characterized. [AAMM]Am-TFSI (3) with two allyl groups showed the widest electrochemical stability window (5.9 V) among the ammonium-based ILs reported to date because [...] Read more.
Several new acyclic ammonium-TFSI ionic liquids with an allyl substituent(s) were synthesized and their physicochemical and electrochemical properties were characterized. [AAMM]Am-TFSI (3) with two allyl groups showed the widest electrochemical stability window (5.9 V) among the ammonium-based ILs reported to date because of the increment of both the anodic and cathodic limits. The charge-discharge performance of a LiCoO2-based half-cell containing [AAMM]Am-TFSI as an electrolyte was better in cycleability (the capacity retention ratio: 99% after 20 cycles) than that of the cell with the corresponding partially saturated analogue, [AMMP]Am-TFSI (2) (the capacity retention ratio: 92% after 20 cycles). Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessArticle Non-Equilibrium Thermodynamic Analysis of Transport Properties in the Nanofiltration of Ionic Liquid-Water Solutions
Molecules 2009, 14(5), 1781-1788; doi:10.3390/molecules14051781
Received: 1 April 2009 / Revised: 18 April 2009 / Accepted: 27 April 2009 / Published: 11 May 2009
Cited by 6 | PDF Full-text (241 KB)
Abstract
Thenanofiltration of aqueous solutions of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), and 1-butyl-3-methylimidazolium bromide ([Bmim]Br) with a polyamide nanofiltration membrane was investigated. The practical transport coefficients, including hydrodynamic permeability (Lp), reflection (σ) and solute [...] Read more.
Thenanofiltration of aqueous solutions of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), and 1-butyl-3-methylimidazolium bromide ([Bmim]Br) with a polyamide nanofiltration membrane was investigated. The practical transport coefficients, including hydrodynamic permeability (Lp), reflection (σ) and solute permeability (ω) were calculated in terms of a non-equilibrium thermodynamics approach. It was found that Lp and σ diminished as the concentration of the IL solutions increased. These characteristics are similar to those observed in inorganic electrolyte-water systems. In addition, it was shown that the rejection and volume flux for both ionic liquid solutions rose with feed pressure, while it decreased with feed concentration. The maximum rejection efficiencies for [Bmim]Br and [Bmim]BF4 are 67 % and 60 %, respectively, on our experimental scale. All the data suggests that a highly efficient process for IL separation could be developed when the operating conditions are optimized further. Full article
(This article belongs to the Special Issue Ionic Liquids)

Review

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Open AccessReview Ionic Liquids — Promising but Challenging Solvents for Homogeneous Derivatization of Cellulose
Molecules 2012, 17(6), 7458-7502; doi:10.3390/molecules17067458
Received: 11 May 2012 / Revised: 5 June 2012 / Accepted: 6 June 2012 / Published: 15 June 2012
Cited by 77 | PDF Full-text (1121 KB)
Abstract
In the past decade, ionic liquids (ILs) have received enormous interest as solvents for cellulose. They have been studied intensively for fractionation and biorefining of lignocellulosic biomass, for dissolution of the polysaccharide, for preparation of cellulosic fibers, and in particular as reaction [...] Read more.
In the past decade, ionic liquids (ILs) have received enormous interest as solvents for cellulose. They have been studied intensively for fractionation and biorefining of lignocellulosic biomass, for dissolution of the polysaccharide, for preparation of cellulosic fibers, and in particular as reaction media for the homogeneous preparation of highly engineered polysaccharide derivatives. ILs show great potential for application on a commercial scale regarding recyclability, high dissolution power, and their broad structural diversity. However, a critical analysis reveals that these promising features are combined with serious drawbacks that need to be addressed in order to utilize ILs for the efficient synthesis of cellulose derivatives. This review presents a comprehensive overview about chemical modification of cellulose in ILs. Difficulties encountered thereby are discussed critically and current as well as future developments in this field of polysaccharide research are outlined. Full article
(This article belongs to the Special Issue Ionic Liquids)
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Open AccessReview Ionic Liquid Applications in Peptide Chemistry: Synthesis, Purification and Analytical Characterization Processes
Molecules 2012, 17(4), 4158-4185; doi:10.3390/molecules17044158
Received: 17 February 2012 / Revised: 22 March 2012 / Accepted: 28 March 2012 / Published: 5 April 2012
Cited by 19 | PDF Full-text (571 KB) | HTML Full-text | XML Full-text
Abstract This review aims to provide a comprehensive overview of the recent advances made in the field of ionic liquids in peptide chemistry and peptide analytics. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessReview Recent Applications of Ionic Liquids in Separation Technology
Molecules 2010, 15(4), 2405-2426; doi:10.3390/molecules15042405
Received: 4 March 2010 / Revised: 29 March 2010 / Accepted: 2 April 2010 / Published: 5 April 2010
Cited by 192 | PDF Full-text (345 KB)
Abstract
Ionic liquids (ILs) have been applied in different areas of separation, such as ionic liquid supported membranes, as mobile phase additives and surface-bonded stationary phases in chromatography separations and as the extraction solvent in sample preparations, because they can be composed from [...] Read more.
Ionic liquids (ILs) have been applied in different areas of separation, such as ionic liquid supported membranes, as mobile phase additives and surface-bonded stationary phases in chromatography separations and as the extraction solvent in sample preparations, because they can be composed from various cations and anions that change the properties and phase behavior of liquids. Although the applications of ILs in separations are still in their early stages, the academic interest in ILs is increasing. An overview of the principle applications of ILs in separation technology is present in this work. Furthermore, the prospects of the ILs in separation techniques are discussed. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessReview On the Chemical Stabilities of Ionic Liquids
Molecules 2009, 14(9), 3780-3813; doi:10.3390/molecules14093780
Received: 1 July 2009 / Revised: 16 September 2009 / Accepted: 18 September 2009 / Published: 25 September 2009
Cited by 179 | PDF Full-text (365 KB)
Abstract
Ionic liquids are novel solvents of interest as greener alternatives to conventional organic solvents aimed at facilitating sustainable chemistry. As a consequence of their unusual physical properties, reusability, and eco-friendly nature, ionic liquids have attracted the attention of organic chemists. Numerous reports [...] Read more.
Ionic liquids are novel solvents of interest as greener alternatives to conventional organic solvents aimed at facilitating sustainable chemistry. As a consequence of their unusual physical properties, reusability, and eco-friendly nature, ionic liquids have attracted the attention of organic chemists. Numerous reports have revealed that many catalysts and reagents were supported in the ionic liquid phase, resulting in enhanced reactivity and selectivity in various important reaction transformations. However, synthetic chemists cannot ignore the stability data and intermolecular interactions, or even reactions that are directly applicable to organic reactions in ionic liquids. It is becoming evident from the increasing number of reports on use of ionic liquids as solvents, catalysts, and reagents in organic synthesis that they are not totally inert under many reaction conditions. While in some cases, their unexpected reactivity has proven fortuitous and in others, it is imperative that when selecting an ionic liquid for a particular synthetic application, attention must be paid to its compatibility with the reaction conditions. Even though, more than 200 room temperature ionic liquids are known, only a few reports have commented their effects on reaction mechanisms or rate/stability. Therefore, rather than attempting to give a comprehensive overview of ionic liquid chemistry, this review focuses on the non-innocent nature of ionic liquids, with a decided emphasis to clearly illuminate the ability of ionic liquids to affect the mechanistic aspects of some organic reactions thereby affecting and promoting the yield and selectivity. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessReview Ionic Liquids as Advanced Lubricant Fluids
Molecules 2009, 14(8), 2888-2908; doi:10.3390/molecules14082888
Received: 17 July 2009 / Revised: 30 July 2009 / Accepted: 3 August 2009 / Published: 4 August 2009
Cited by 238 | PDF Full-text (450 KB) | HTML Full-text | XML Full-text
Abstract
Ionic liquids (ILs) are finding technological applications as chemical reaction media and engineering fluids. Some emerging fields are those of lubrication, surface engineering and nanotechnology. ILs are thermally stable, non-flammable highly polar fluids with negligible volatility, these characteristics make them ideal candidates [...] Read more.
Ionic liquids (ILs) are finding technological applications as chemical reaction media and engineering fluids. Some emerging fields are those of lubrication, surface engineering and nanotechnology. ILs are thermally stable, non-flammable highly polar fluids with negligible volatility, these characteristics make them ideal candidates for new lubricants under severe conditions, were conventional oils and greases or solid lubricants fail. Such conditions include ultra-high vacuum and extreme temperatures. Other very promising areas which depend on the interaction between IL molecules and material surfaces are the use of ILs in the lubrication of microelectromechanic and nanoelectromechanic systems (MEMS and NEMS), the friction and wear reduction of reactive light alloys and the modification of nanophases. Full article
(This article belongs to the Special Issue Ionic Liquids)
Open AccessReview Ionic Liquids in Tribology
Molecules 2009, 14(6), 2286-2305; doi:10.3390/molecules14062286
Received: 24 May 2009 / Revised: 20 June 2009 / Accepted: 23 June 2009 / Published: 24 June 2009
Cited by 251 | PDF Full-text (605 KB)
Abstract
Current research on room-temperature ionic liquids as lubricants is described. Ionic liquids possess excellent properties such as non-volatility, non-flammability, and thermo-oxidative stability. The potential use of ionic liquids as lubricants was first proposed in 2001 and approximately 70 articles pertaining to fundamental [...] Read more.
Current research on room-temperature ionic liquids as lubricants is described. Ionic liquids possess excellent properties such as non-volatility, non-flammability, and thermo-oxidative stability. The potential use of ionic liquids as lubricants was first proposed in 2001 and approximately 70 articles pertaining to fundamental research on ionic liquids have been published through May 2009. A large majority of the cations examined in this area are derived from 1,3-dialkylimidazolium, with a higher alkyl group on the imidazolium cation being beneficial for good lubrication, while it reduces the thermo-oxidative stability. Hydrophobic anions provide both good lubricity and significant thermo-oxidative stability. The anions decompose through a tribochemical reaction to generate metal fluoride on the rubbed surface. Additive technology to improve lubricity is also explained. An introduction to tribology as an interdisciplinary field of lubrication is also provided. Full article
(This article belongs to the Special Issue Ionic Liquids)

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