Compounds In Ionic Liquids Research Articles

The electrochemistry of simple inorganic molecules in room temperature ionic liquids

The electrochemistry of simple inorganic compounds in room temperature ionic liquids (RTILs) is reviewed and some new work in this area is presented. This paper focuses on the comparison between electrochemical behaviour in RTILs and in conventional aprotic solvents. Some compounds (iodides, O2, NO2, SO2, NH3) display similar reactions and mechanisms in RTILs as in aprotic solvents (as is observed for organic compounds). However other species (nitrates, PCl3, POCl3) show remarkably different behaviour to traditional solvents. This makes RTILs very promising media for the study of inorganic compounds, and highlights the need for more investigations in this exciting area.

Oxidation of unsaturated compounds in ionic liquids with the use of cyclodextrin-containing catalytic systems

The Wacker oxidation of alkenes-1 in ionic liquids catalyzed by a system containing palladium, and copper complexes and β-cyclodextrins was studied. It was shown that the use of β-cyclodextrins substantially increases the oxidation rate in biphasic systems olefin/ionic liquid. It was found that the proposed catalytic systems possess substrate selectivity, which is determined by the structure of a receptor molecule.

Effect of different reaction parameters on the lipase-catalyzed selective acylation of polyhydroxylated natural compounds in ionic liquids

The effect of various reaction parameters on the enzymatic acylation of plant polyhydroxylated compounds, including phenolic and flavonoid glucosides (salicin, helicin, esculin and naringin), was investigated in imidazolium-based ionic liquids (1-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF 4 and 1-butyl-3-methylimidazolium hexafluorophosphate [bmim]PF 6), using immobilized lipase B from Candida antarctica. The conversion yield, the regioselectivity and the reaction rate of the biocatalytic process strongly depended on the ionic liquid used, their water content, the incubation temperature, as well as the solubility and the concentration of substrates. For most glucosides tested, one major product (monoacylated derivative) was detected as a result of the acylation of the primary hydroxyl group of glucose moiety. The acylation rate and the regioselectivity of the process are higher in [bmim]BF 4, where the solubility of all glucosides is significantly higher than in [bmim]PF 6 or acetone. Response surface methodology (RSM) based on a five level-three variable central composite circumscribed design, was employed to evaluate the interactive effect of the molar ratio of substrates (MR), the initial concentration of glucoside (N) and the reaction time (RT), as well as for their optimization in [bmim]BF 4. At the optimal reaction conditions the maximum acylation yield was 87%. The amount of monoacylated derivatives produced in a single-step biocatalytic process reached values up to 31.6 g/l which is considerably higher than those reported for organic media.

Electrophilic Reactions of Aromatic and Heteroaromatic Compounds in Ionic Liquids

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Electrophilic reactions of aromatic and heteroaromatic compounds in ionic liquids

The review summarizes and analyzes published data on electrophilic aromatic substitution reactions performed in ionic liquids.

Dehydrogenation of Unsymmetric Hydrazo Compounds in Ionic Liquid: Novel Green Synthesis of Azo Compounds

Using NBS (N-bromosuccinimide) and the ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) as an oxidation system, twelve unsymmetric azo compounds were efficiently prepared from hydrazo compounds for the first time. In contrast to the known methods, this novel access to azo compounds presented here is operationally simple, environmentally benign and has the advantage of enhanced atom utilization. Furthermore, the solvent and the basic catalyst used can be recovered conveniently and reused efficiently.

Ionic Liquid Promoted Synthesis of β-Enamino Ketones at Room Temperature

β-Enamino ketones have been synthesised in excellent yield at room temperature in the absence of any added catalyst by the reaction of aromatic or aliphatic amines with 1,3-dicarbonyl compounds in ionic liquid. The ionic liquid is recycled and reused several times.

Trihalide‐Based Imidazolium Salts as Versatile Reagents for the Halogenation of Unsaturated Compounds in Ionic Liquids

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access the actual ChemInform Abstract, please click on HTML or PDF.

Heterogeneous electron-transfer kinetics of nitro compounds in room-temperature ionic liquids

The influence of using room temperature ionic liquids on the heterogeneous electron transfer kinetics has been investigated with the example of the reduction of a series of nitro aromatic and aliphatic compounds. The standard electron transfer kinetic rate constants, k s, were measured in two ionic liquids (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and triethylbutylammonium bis(trifluoromethylsulfonyl)imide) and compared with the same data determined in acetonitrile. For the fastest redox couples (nitrobenzene derivatives) for which the outer sphere contribution to the activation energy is the major factor controlling the electron transfer, the values of k s considerably decrease in the ionic liquids (at least 2 orders of magnitude). On the contrary, when the inner sphere contribution is large, for example for the reduction of the 2-methyl-2-nitropropane, the k s shows negligible variations when passing in the ionic liquid. For aromatic molecules, the amplitude of the kinetics slowness is inversely proportional to the steric hindrance introduced around the NO 2 group.

Oxidative self-coupling of aromatic compounds in ionic liquids

Electrochemical oxidation of mononuclear (anisole, mesitylene) and fused polynuclear (naphthalene, anthracene) aromatic compounds was performed in various ionic liquids (ILs) to provide the products of anodic dimerization. Under similar conditions, the process with 1,2-dimethoxybenzene resulted in polyveratrole, stable blue-colored doped polymer of amorphous or fibrillar morphology depending on the IL used as the electrolytic media. The electrosyntheses of anodic self-coupling products in ILs were realized in an undivided cell when the paired reaction at the auxiliary electrode was the reduction of protons eliminated in the target anodic process.

Highly Selective Electrochemical Fluorination of Organic Compounds in Ionic Liquids

AbstractFor Abstract see ChemInform Abstract in Full Text.

Kinetic study of the addition of trihalides to unsaturated compounds in ionic liquids. Evidence of a remarkable solvent effect in the reaction of ICl2-.

The kinetic constants and activation parameters for the reactions of Br(3)(-) and ICl(2)(-) with some alkenes and alkynes have been determined in the ionic liquids [bmim][PF(6)], [emim][Tf(2)N], [bmim][Tf(2)N], [hmim][TF(2)N], [bm(2)im][Tf(2)N], and [bpy][TF(2)N] (where emim = 1-ethyl-3-methylimidazolium, bmim = 1-butyl-3-methylimidazolium, hmim = 1-hexyl-3-methylimidazolium, bm(2)im = 1-butyl-2,3-dimethylimidazolium, bpy = butylpyridinium, PF(6) = hexafluorophosphate, and Tf(2)N = bis(trifluoromethylsulfonyl)imide) and in 1,2-dichloroethane. The rates of both reactions increase on going from 1,2-dichloroethane to ILs. Evidence suggests that, while the hydrogen bonding ability of the imidazolium cation is probably the main factor able to increase the rate of the addition of ICl(2)(-) to double and triple bonds, this property has no effect on the electrophilic addition of Br(3)(-) to alkenes and alkynes. Furthermore, in the case of the ICl(2)(-) reaction, the hydrogen bonding ability of ILs can be exploited to suppress the unwanted nucleophilic substitution reaction on the products by the Cl(-) anion.

An Effective Approach for the Silylation of Hydroxyl Compounds in Room Temperature Ionic Liquids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

On the catalytic activity of cluster anions in styrene hydrogenation: considerable enhancements in ionic liquids compared to molecular solvents

Many low oxidation state transition metal (carbonyl) clusters are salts and are highly soluble in ionic liquids. Since many are also effective catalysts/precatalysts for hydrogenation reactions, we have conducted a catalytic study of these compounds in ionic liquids and found that the activity of certain clusters to hydrogenate alkene substrates, when immobilised in ionic liquids, is up to 3.6-fold faster than that observed in organic solvents. Using high-pressure NMR it has been possible to trace the improvements in activity to the increased stability of the cluster species in the ionic liquid. The ionic liquid also gives rise to higher regioselectivity in the hydrogenation of cyclic dienes to monoenes compared to that observed in organic solvents.

Chemoselective Reduction of Aromatic Nitro and Azo Compounds in Ionic Liquids Using Zinc and Ammonium Salts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An Effective Approach for the Silylation of Hydroxyl Compounds in Room Temperature Ionic Liquids

The room temperature ionic liquid (RTIL) 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) is used as a “green” recyclable alternative to conventional solvents for the silylation of a series of hydroxyl compounds (alcohols and phenols) with t-butyldimethylchlorosilane (TBDMCS), which has some advantages such as simplicity of the synthetic procedure, the potential for recycling of the ionic liquid and the environmentally benign.

Mukaiyama aldol reaction using ketene silyl acetals with carbonyl compounds in ionic liquids

Mukaiyama aldol reactions using ketene silyl acetals with various aldehydes proceed smoothly in ionic liquids to afford the corresponding aldol products in moderate yields.

Chemoselective reduction of aromatic nitro and azo compounds in ionic liquids using zinc and ammonium salts

Nitroarenes were chemoselectively reduced to the corresponding amines using zinc and aqueous ammonium salts in ionic liquids as a safe and recyclable reaction medium. Our results specify the effect of ammonium salts in the process; the combination of Zn/NH 4 Cl in [bmim][PF 6 ] or Zn/HCO 2 NH 4 in [bmim][BF 4 ] were the suitable conditions for the reduction of nitroarenes. Azobenzenes were also smoothly reduced to hydrazobenzenes with Zn/HCO 2 NH 4 (aq.) in recyclable [bmim][BF 4 ] without any over reduction to the corresponding anilines.

Why are aromatic compounds more soluble than aliphatic compounds in dimethylimidazolium ionic liquids? A simulation study

Molecular dynamics simulations of solutions of benzene in dimethylimidazolium chloride and dimethylimidazolium hexafluorophosphate have been performed with a view to answering the question posed in the title. The difference between the chemical potential of a normal model of benzene and one with no charges was found to depend on the solvent but is at least 4 k B T. This difference is sufficient to account for the observed solubility differences. There are substantial changes in the local structure around benzene with and without charges.

Prediction of Infinite Dilution Activity Coefficients of Organic Compounds in Ionic Liquids Using COSMO-RS

COSMO-RS, a general and fast method for the prediction of thermophysical data of liquids, is used for the calculation of activity coefficients at infinite dilution for 38 compounds in the ionic liquids 1-methyl-3-ethylimidazolium bis((trifluoromethyl)sulfonyl)imide, 1,2-dimethyl-3-ethylimidazolium bis((trifluoromethyl)sulfonyl)imide, and 4-methyl-N-butylpyridinium tetrafluoroborate. Calculated values for (314 and 344) K are presented and compared with experimental data.