Acidic Room Temperature Ionic Liquid Research Articles

Alkylsulfuric acid ionic liquids: a promising class of strongly acidic room-temperature ionic liquids.

Strongly acidic (pKa ≈ -3.5) room-temperature ionic liquids (ILs) with -OSO3H functionalized cations are introduced. The strong acidity, easy synthesis, and better physical properties of these R-OSO3H ILs make them excellent alternatives to the well-known sulfonic acid (R-SO3H) ILs, especially in the domain of metal processing.

Green synthesis of photoactive nanocrystalline anatase TiO2 in recyclable and recoverable acidic ionic liquid [Bmim] HSO4

This is the first report of a facile and green method for the synthesis of nanocrystalline anatase TiO2 in an acidic room temperature ionic liquid 1-buty-3-methylimidazolium hydrogen sulphate [Bmim] HSO4 as an acidic hydrolysing and templating/structure directing agent avoiding the use of corrosive mineral acids and surfactants, respectively. The effect of calcination temperature was studied at 100, 350, 550 and 750 °C to obtain samples S-1 to S-4, respectively, and the effect on morphology, phase, surface area and band gap of TiO2 was investigated using XRD, TEM, (UV–Vis) diffuse reflectance spectroscopy, BET surface area and Raman spectroscopic techniques. It was observed that with an increase in temperature of calcination, the phase of TiO2 nanoparticles remained anatase, while the morphology of the particles was both spherical and cubic in nature with particle size varying between 4 and 30 nm. The ionic liquid used was both recoverable and recyclable up to three cycles. The photocatalytic activity of the samples was tested for the degradation of methyl orange as the model compound under ultraviolet light. The nanoparticles of TiO2 calcined at 550 °C showed high photocatalytic activity.

Reusable 1,2,4-Triazolium Based Brønsted Acidic Room Temperature Ionic Liquids as Catalyst for Mannich Base Reaction

Unprecedented examples of 1-alkyl-1,2,4-triazolium methanesulfonate based Bronsted acidic room temperature ionic liquids were synthesized and characterized. Their catalytic activity and efficiency in recyclability and reusability on one pot synthesis of halide substituted β-amino carbonyl compounds are reported.

Bmim][InCl4]-Catalyzed Addition of Hydrazones to β-Diketones: An Efficient Regioselective Synthesis of Pyrazoles and Pyrazole-Fused Cyclohexanones

The Lewis acidic room-temperature ionic liquid, [bmim][InCl 4 ], was found to be an efficient catalyst for the regio­selective synthesis of fully substituted pyrazoles and pyrazole-fused cyclohexanones through condensation of hydrazones with symmetrical and unsymmetrical 1,3-diketones. This procedure is simple, ­affording the corresponding products in good to high yields.

A facile and economical procedure for the synthesis of maleimide derivatives using an acidic ionic liquid as a catalyst

Seven maleimide derivatives were synthesized in good yields and high purity from the corresponding maleamic acids using a Brønsted acidic room temperature ionic liquid (RTIL) as a catalyst. The products were obtained through merely a decanting and removal of the solvent, suggesting that this procedure is superior to the conventional routes, in which the strong organic/inorganic acids were used as the catalysts, as well as a complicated post-processing procedure for the separation and purification of the products was employed.

A new type of unsaturated polyester resin with low dielectric constant and high thermostability: preparation and properties

A new type of unsaturated polyester resins (UP) with low dielectric constant (κ) and high thermostability was prepared by doping N-phenylmaleimides containing perfluoroalkyl substituents (–CF3 and –C6F13) into a commercial unsaturated polyester resin. In comparison with neat UP resin, the doped UP resins showed decreased dielectric constant and increased char yields. The best result was obtained when the substituent was –CF3, which gave a dielectric constant of 3.63 and 5 wt%, loss temperature of 336 °C with a char yield of 5.57% under N2. Such data are superior to those of neat UP resin, which showed dielectric constants of 4.38 and 5 wt%, a loss temperature of 327 °C with a char yield of 2.25% . In this contribution, a new environmentally-friendly procedure for the synthesis of the fluoro-containing maleimides was also provided, in which a Bronsted acidic room temperature ionic liquid was employed as a catalyst and the products were obtained through merely decanting and removal of the solvent.

Application of a multi-SO3H Brønsted acidic ionic liquid in water: a highly efficient and reusable catalyst for the regioselective and scaled-up synthesis of pyrazoles under mild conditions

An elegant and efficient procedure with exceptionally mild conditions for the regioselective synthesis of pyrazoles by the reaction of various 1,3-diketones and hydrazines/hydrazides using a multi-SO3H Bronsted acidic room temperature ionic liquid as a powerful catalyst in aqueous media has been developed. The ionic liquid was easily separated from the reaction mixture and was recycled and used for at least six consecutive runs without any loss of activity.

High conductivity and low viscosity Brønsted acidic ionic liquids with oligomeric anions

Two series of Brønsted acidic room temperature ionic liquids (RTILs) comprising of oligomeric anions and cyclic amine based cations are prepared. All RTILs studied here are liquids and have a high ionic conductivity (up to 20.96 mS/cm) and a low viscosity (down to 10.4 mPa s) at room temperature. The incorporation of oligomeric anions in ILs significantly increases the density and conductivity, and decreases the viscosity. The temperature-dependent electrolyte viscosity with molar conductivity is correlated through applying an empirical Walden's rule. A relatively larger deviation of the plots from the “ideal” Walden line is observed for the ILs synthesized by equal molar acid and base, although the deviation decreases significantly when the ILs contain oligomeric anions. Spectroscopic measurements of solvatochromic probe molecules in RTILs provide insights into solvent intermolecular interactions through interpretation of the different and generally uncorrelated polarity scales.

Desulfurization by oxidation combined with extraction using acidic room-temperature ionic liquids

Room-temperature ionic liquids (ILs) are commonly used for desulfurization by extraction for their unique solvent characteristics. In this study, 1-ethyl-3-(4-sulfobutyl)imidazolium bis(trifluoromethanesulfonyl)imide ([EimC4SO3H]NTf2) was used as catalyst and extractant for desulfurization of DBT in n-octane. The results show that dibenzothiophene (DBT) could be removed from the oil phase effectively by this process, and that the sulfur content in a model oil could be decreased from 1600 ppm to less than 20 ppm. The extraction efficiency of the IL was greatly influenced by the structure of the anions and cations. The order of extraction capability of ILs was [EimC4SO3H]NTf2 > [EimC4SO3H]HSO4 > [C4Py]NTf2 > [Bmim]NTf2 > [Bmim]PF6. Experiments on the recycling and reuse of the room-temperature IL were also performed, and we found that [EimC4SO3H]NTf2 could be recycled 5 times without significant decrease in the desulfurization activity. The extraction mechanism was also probed in detail, and we found that DBT was oxidized to its corresponding sulfone by H2O2 and NaClO, which was then extracted by the IL phase. However, different extraction mechanisms are at work with different oxidants.

C4mim][InCl4]: An efficient catalyst-medium for alkoxymethylation of alcohols and their interconversion to acetates and TMS-ethers

Abstract A simple, green and chemoselective method for methoxymethylation and ethoxymethylation of primary and secondary alcohols using a Lewis acidic room temperature ionic liquid, [C4mim][InCl4], as catalyst and reaction medium under ambient temperature, microwave and ultrasonic irradiations is reported. In this catalytic system, the corresponding MOM-and EOM-ethers are obtained in excellent yields and in short reaction times. Furthermore, this catalytic system was used for mild and efficient transformations of these protected alcohols to their corresponding acetates and trimethylsilyl ethers under thermal conditions and microwave and ultrasonic irradiations.

Microwave-assisted rapid and efficient deprotection and direct esterification and silylation of MOM and EOM ethers catalyzed by [Hmim][HSO4] as a Brønsted acidic ionic liquid

1-Methylimidazolium hydrogensulfate, [Hmim][HSO4], a Bronsted acidic room temperature ionic liquid, is used as a catalyst and reaction medium for facile and eco-friendly deprotection of methoxymethyl (MOM) and ethoxymethyl (EOM) ethers to their corresponding alcohols under thermal conditions (Δ) and microwave irradiation (MW). Furthermore, one-pot interconversion to the respective acetates and trimethylsilyl (TMS) ethers was also achieved.

Structure of the Room-Temperature Ionic Liquid 1-Hexyl-3-methylimidazolium Hydrogen Sulfate: Conformational Isomerism

The acidic room-temperature ionic liquid 1-hexyl-3-methylimidazolium hydrogen sulfate has recently been identified to have beneficial properties for practical applications in catalysis and electrochemistry. In the present work, the conformational isomerism of this ionic liquid is studied by means of density functional theory calculations and experiments in terms of infrared absorption and Raman scattering spectroscopy. For the hydrogen sulfate anion, the trans conformer is found to be the favored isomer in the ionic liquid. For the 1-hexyl-3-methylimidazolium cation, three different low-energy conformations were obtained, differing only in the orientation of the hexyl chain. The comparison of vibrational frequencies with IR and Raman data showed good agreement for all three conformations, indicating their presence in the ionic liquid. Beyond revealing the conformational information, the experimental spectra indicate strong interionic interactions. Vibrations of sulfuric acid could be observed, indicating possible proton transfer from the cation to the anion. This is further supported by the appearance of modes around 2000 cm(-1) in the IR spectrum, which could tentatively be assigned to C2-H stretching vibrations red-shifted as a result of strong interionic hydrogen bonds as a prerequisite of proton transfer.

Brönsted Acidic Ionic Liquid as an Efficient Catalyst for Acetylation of Alcohols and Phenols

AbstractA novel Brönsted acidic room temperature ionic liquid (1‐H‐3‐methyl‐imidazolium bisulfate) is found to catalyze efficiently the acetylation of a wide rang of alcohols as well as phenols with acetic anhydride in good to excellent yields at 50°C under solvent‐free conditions. Products are easily isolated by extraction with ether and the protocol is mild and green, compared to the existing method based on toxic solvents.

Synthesis of 2,4,5-trisubstituted imidazoles catalyzed by [Hmim]HSO4 as a powerful Brönsted acidic ionic liquid

An efficient and green procedure for the synthesis of 2,4,5-trisubstituted imidazoles with various aldehydes using a catalytic amount of 1-methylimidazolium hydrogenesulfate as an active and low cost Brönsted acidic room temperature ionic liquid has been developed. The ionic liquid was easily separated from the reaction mixture and was recycled five times without any loss in activity.Key words: ionic liquid, 2,4,5-trisubstituted imidazoles, [Hmim]HSO4, aldehyde, benzil.

Progress in Surface Finishing with Lewis Acidic Room-Temperature Chloroaluminate Ionic Liquids

In this article, we survey the progress that has been attained to date in the area of surface finishing with solvents derived from Lewis acidic room-temperature chloroaluminate ionic liquids, such as AlCl3-1-ethyl-3-methylimidazolium chloride and AlCl3-1-(1-butyl)pyridinium chloride. This field of study has received constant attention since the late 1970's. For descriptive purposes, the surface finishing technology associated with these ionic liquids is divided into four categories: Al plating, underpotential plating of binary Al alloys, overpotential plating of binary Al alloys, and overpotential plating of ternary Al alloys. We include in this report recent experimental results describing the electrodeposition of AlHf, AlW, and AlInSb alloys from the 66.7-33.3 mole percent AlCl3-1-ethyl-3-methylimidazolium chloride ionic liquid.

Synthesis of multi-hydroxyl and sulfonyl dual-functionalized room temperature ionic liquids

Starting from the hydroxylamine (dimethyl amino ethanol, triethanolamine) and 1,3-propane sultone, a series of hydroxyl and sulfonyl dual-functionalized zwitterionic salts and corresponding acidic room temperature ionic liquids have been synthesized. The hydroxyl groups of the synthesized substances were confirmed by the 1H NMR measurement. These zwitterionic salts and ionic liquids may be used for synthesizing other functionalized ionic liquids or ionic liquid-polymer (polyelectrolyte).

Brönsted acidic ionic liquid as an efficient catalyst for chemoselective synthesis of 1,1-diacetates under solvent-free conditions

Abstract We introduce a simple and efficient procedure for preparation of (1-H-3-methyl-imidazolium hydrogen sulfate) as a Bronsted acidic ionic liquid using 1-methylimidazole in the presence of concentrated sulfuric acid. Further, this Bronsted acidic room temperature ionic liquid has been employed as a catalyst for the synthesis of 1,1-diacetates from aldehydes under mild and solvent-free conditions at room temperature.

Brønsted acidic room temperature ionic liquids derived from N,N-dimethylformamide and similar protophilic amides

We herein describe a convenient and efficient one-pot route to a new family of cost-effective, highly proton conductive room temperature ionic liquids based on N,N-dimethylformamide and structural analogues thereof, thereby opening up potential in the fuel cell industry and other areas.

Properties of Asymmetric Benzyl-Substituted Ammonium Ionic Liquids and Their Electrochemical Properties

Benzyl-substituted quaternary ammonium ions were used to form room-temperature ionic liquids with chloroaluminate ions. Asymmetric ammonium structures significantly lowered the melting point of the ionic liquid. Asymmetric benzyl-substituted ammonium chlorides were mixed with to form acidic room-temperature ionic liquids. It is shown that the melting point and viscosity are a function of the symmetry of the quaternary ammonium ion and its molecular weight. Asymmetry and low molecular weight favor lower viscosity and melting point, and higher conductivity. These liquids were neutralized with NaCl and tested as electrolytes for sodium batteries. The neutralized ionic liquid of benzyldimethylethylammonium chloride had a low self-discharge current (3.96 μA/cm2) at room temperature on a platinum electrode substrate. © 2005 The Electrochemical Society. All rights reserved.

Microwave accelerated preparation of [bmim][HSO 4] ionic liquid: an acid catalyst for improved synthesis of coumarins

A efficient and easy method for preparation of (1-butyl-3-methyl-imidazolium hydrogen sulphate) ionic liquid using sodium bisulphate in place of concentrated sulphuric acid by microwave irradiation had been developed by us with manifold reduction in time. Further, this acidic room temperature ionic liquid has been exploited for the synthesis of coumarins under microwave irradiation and solventless conditions in short duration of time with quantitative yields, for the first time.