分子模拟研究气体在室温离子液体中的溶解度

在作者先前建立的分子力场基础上, 采用Widom粒子插入法预测了CO₂、N₂、O₂、Ar及CH₄等5种气体在多种咪唑类离子液体中的溶解度, 包括2种侧链长度的阳离子和3种阴离子. 首先考察了256个离子对组成的体系中溶质分子插入次数对计算结果的影响, 在此基础上计算了不同温度下气体在1-丁基-3-甲基咪唑的四氟化硼盐([bmim][BF₄])和六氟化磷盐([bmim][PF₆])中的溶解度. 计算结果正确反映了CO₂气体溶解度的变化趋势, 在[bmim][BF₄]中溶解度的模拟结果与实验值符合很好, 且明显优于Pádua等的模拟结果；在[bmim][PF₆]中的溶解度较实验值偏高, 精度与文献模拟结果相当；并预测了较高温度下CO₂气体在[bmim][BF₄]和[bmim][PF₆]中的溶解度. 计算结果也正确地反映了5种气体在[bmim][PF₆]中溶解度实验值的相对大小. 另外考察了常温下几种气体在不同室温离子液体中的溶解度, 模拟结果表明气体在含有较长碳链和双-三氟甲基磺酰胺阴离子(Tf₂N^－)的离子液体中溶解度较大.     

Density and viscosity of three (2,2,2-trifluoroethanol + 1-butyl-3-methylimidazolium) ionic liquid binary systems

Densities and viscosities were determined for binary mixtures of 2,2,2-trifluoroethanol (TFE) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) or 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([bmim][NTf₂]) over the entire range of composition. The experimental measurements were carried out at temperatures ranging from 278.15 K to 333.15 K, at atmospheric pressure. The densities and viscosities of the pure ionic liquids and their mixtures with TFE were described successfully by an empirical third-order polynomial and by the Vogel–Fulcher–Tammann equation, respectively. In addition, excess molar volumes and viscosity deviations were determined from densities and viscosities of mixtures, respectively, and fitted by using the Redlich–Kister equation.     

Study of aromatic nucleophilic substitution with amines on nitrothiophenes in room-temperature ionic liquids: are the different effects on the behavior of para-like and ortho-like isomers on going from conventional solvents to room-temperature ionic liquids related to solvation effects?

The kinetics of the nucleophilic aromatic substitution of some 2-L-5-nitrothiophenes (para-like isomers) with three different amines (pyrrolidine, piperidine, and morpholine) were studied in three room-temperature ionic liquids ([bmim][BF4], [bmim][PF6], and [bm(2)im][BF4], where bmim = 1-butyl-3-methylimidazolium and bm(2)im = 1-butyl-2,3-dimethylimidazolium). To calculate thermodynamic parameters, a useful instrument to gain information concerning reagent-solvent interactions, the reaction was carried out over the temperature range 293-313 K. The reaction occurs faster in ionic liquids than in conventional solvents (methanol, benzene), a dependence of rate constants on amine concentration similar to that observed in methanol, suggesting a parallel behavior. The above reaction also was studied with 2-bromo-3-nitrothiophene, an ortho-like derivative able to give peculiar intramolecular interactions in the transition state, which are strongly affected by the reaction medium.     

[Bmim]PF6 and BF4 ionic liquids as novel and recyclable reaction media for aromatic amination

Activated aryl halides undergo smooth nucleophilic substitution reactions with secondary amines in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF₆) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF₄) ionic liquids (ILs) at room temperature to afford the corresponding arylamines in excellent yields under mild and neutral conditions.     

Ionic liquids/[bmim][N3] mixtures: promising media for the synthesis of aryl azides by SNAr

The nucleophilic aromatic substitution of some activated aryl or heteroaryl halides has been performed in ionic liquid solution, using the 1-butyl-3-methylimidazolium azide as a nucleophile. The reaction course was studied varying the structures of both substrates and ionic liquids. In particular, in the latter case, the reaction of 2-bromo-5-nitrothiophene was carried out in five different ionic liquids ([bmim][BF 4], [bmim][PF 6], [bmim][NTf 2], [bm 2im][NTf 2], and [bmpyrr][NTf 2]). Finally, for all the substrates considered, a comparison with data obtained in MeOH solution in the presence of NaN 3 was also performed. Data collected indicate that in some cases it is possible to obtain aromatic or heteroaromatic azide derivatives in satisfactory yield by means of a S NAr reaction using [bmim][N 3] as the nucleophile.     

Densities and viscosities for ionic liquids mixtures containing [eOHmim][BF4], [bmim][BF4] and [bpy][BF4]

Densities and viscosities of binary ionic liquids mixtures, 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([eOHmim][BF₄]) + 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([eOHmim][BF₄]) + N-butylpyridinium tetrafluoroborate ([bpy][BF₄]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) + N-butylpyridinium tetrafluoroborate ([bpy][BF₄]) were measured over the entire mole fraction from T = (298.15 to 343.15) K. The excess molar volumes were calculated and correlated by Redlich–Kiser polynomial expansions. The viscosities for pure ionic liquids were analyzed by means of the Vogel–Tammann–Fulcher equation and ideal mixing rules were applied for the ILs mixtures.     

Ionic liquid acceleration of solid-phase suzuki-miyaura cross-coupling reactions

[reaction: see text] Room-temperature ionic liquids promote various transition metal-catalyzed reactions in the solution phase. Here, for the first time, we show that these effects are translatable to solid-phase reactions. The Suzuki-Miyaura cross-coupling of 4-iodophenol immobilized on polystyrene-Wang resin with various arylboronic acids was significantly accelerated by the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)(-)]).     

[Bmim]BF4 ionic liquid: a novel reaction medium for the synthesis of β-amino alcohols

Epoxides undergo smooth ring-opening with aryl amines in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF₄) or 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF₆) ionic liquids under mild and neutral conditions to afford the corresponding β-amino alcohols in excellent yields with high regioselectivity.     

离子液体型表面活性剂研究

以1-甲基咪唑为原料, 制备了6个常规离子液体: 1-正丁基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[bmim][BF₄]及[bmim][PF₆])、1-正己基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[hmim][BF₄]及[hmim][PF₆])、1-正十六烷基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[C₁₆mim][BF₄]及[C₁₆mim][PF₆])和4个功能化离子液体: 1-(2-羟乙基)-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[2-hemim][BF₄]及[2-hemim][PF₆])、1-乙氧羰基甲基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[eocmmim][BF₄]及[eocmmim][PF₆]). 研究了这两类离子液体的一些物理性能, 旨在挖掘离子液体在香料香精化妆品工业中的应用价值. 分别检测了它们与一般溶剂的互溶性, 并测定了它们的表面张力和发泡性能, 实验结果表明, 仅[C₁₆mim][BF₄]和[C₁₆mim][PF₆]具有发泡性能, 发泡力分别为68和120 mm.     

Partial molar volumes of selected gases in some ionic liquids

The partial molar volume of a gas that is dissolved at high dilution in a solvent is required to express the influence of pressure on Henry's constant as well as to describe the volume change (expansion) of the liquid caused by the dissolved gas. The correlations of recently published experimental results for the solubility of some selected gases (CO₂, Xe, CH₄, CF₄, H₂, CO, O₂) in three imidazolium-based ionic liquids (1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-n-butyl-3-methylimidazolium methyl sulfate ([bmim][CH₃SO₄]), and 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf₂N])) determined by the synthetic method were re-evaluated by also considering the experimentally determined volumetric properties. The new evaluation does not change the published results for Henry's constants, but additionally yields reliable information on the partial molar volume of those gases in the mentioned ionic liquids at temperatures from about 293 to 413 K.     

Nonsolvent application of ionic liquids: organo-catalysis by 1-alkyl-3-methylimidazolium cation based room-temperature ionic liquids for chemoselective N-tert-butyloxycarbonylation of amines and the influence of the C-2 hydrogen on catalytic efficiency

1-Alkyl-3-methylimidazolium cation based ionic liquids efficiently catalyze N-tert-butyloxycarbonylation of amines with excellent chemoselectivity. The catalytic role of the ionic liquid is envisaged as "electrophilic activation" of di-tert-butyl dicarbonate (Boc(2)O) through bifurcated hydrogen bond formation with the C-2 hydrogen of the 1-alkyl-3-methylimidazolium cation and has been supported by a downfield shift of the imidazolium C-2 hydrogen of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][NTf(2)]) from δ 8.39 to 8.66 in the presence of Boc(2)O in the (1)H NMR and a drastic reduction of the catalytic efficiency with 1-butyl-2,3-dimethylimidazolium ionic liquids that are devoid of the C-2 hydrogen. The differential time required for reaction with aromatic and aliphatic amines has offered means for selective N-t-Boc formation during inter and intramolecular competitions. Preferential N-t-Boc formation with secondary aliphatic amine has been achieved in the presence of primary aliphatic amine. Comparison of the catalytic efficiency for N-t-Boc formation with a common substrate revealed that [bmim][NTf(2)] is superior to the reported Lewis acid catalysts.     

A metallacage encapsulating chloride as a probe for a solvation scale in ionic liquids

With the purpose of assessing the reactivity of chloride ions dissolved in ionic liquids (ILs), a relative scale for the solvation of chloride is given for a series of ILs based on the bis(trifluoromethane)sulfonimide ([Tf(2)N]) anion and different cations, 1-butyl-3-methylimidazolium ([bmim]), 1-butyl-2,3-dimethylimidazolium ([bdmim]), 1-butyl-1-methylpyrrolidinium ([bmpy]), 1-butylpyridinium ([bpy]), 1-pentyl-1,1,1-triethylammonium ([C(5)e(3)am]), and 1-(2-hydroxy)ethyl-3-methylimidazolium ([mimeOH]). Insights into the solvation of chloride are achieved by the thermodynamic study of the reaction of dissociation of a chloride-templated nickel(II) metallacage performed at various temperatures by UV-visible spectroscopy in each IL. The order of chloride solvation [C(5)e(3)am][Tf(2)N] < [bmpy][Tf(2)N] < [bmim][Tf(2)N] 相似文献   

Effect of anionic structure on the phase formation and hydrophobicity of amino acid ionic liquids aqueous two-phase systems

Compared with the conventional ionic liquids, amino acid ionic liquids are more biodegradable and biocompatible, and can enhance stability of biomaterials. In this work, amino acid ionic liquids 1-butyl-3-methylimidazolium L-serine ([C(4)mim][Ser]), 1-butyl-3-methylimidazolium glycine ([C(4)mim][Gly]), 1-butyl-3-methylimidazolium L-alanine ([C(4)mim][Ala]) and 1-butyl-3-methylimidazolium L-leucine ([C(4)mim][Leu]) have been synthesized. These ionic liquids are found to form aqueous two-phase systems (ATPSs) by the salted-out of K(3)PO(4) in aqueous solutions. Phase diagram of the ATPSs and the Gibbs energies of transfer of methylene group from the bottom salt-rich phase to the top ionic liquid-rich phase have been determined at 298.15K and pH 14, and the effect of anionic structure of the ionic liquids on phase formation of the ATPSs and the relative hydrophobicity between the top and the bottom phases are then examined. In order to understand the effect of relative hydrophobicity of the phases in equilibrium in the ATPSs on the extraction/separation capability of biomolecules, the partition coefficients of cytochrome-c (as a model biomolecule) in the ATPSs are measured by spectrophotometry. It is suggested that hydrophobic interactions are mainly responsible for the higher partition coefficients of cytochrome-c in aqueous two-phase systems at pH 14, and the extraction and separation capacity of biomolecules can be improved by the modulation of the relative hydrophobicity of the phases and/or the pH of the system.     

Free Radical Polymerization of Acrylonitrile in Green Ionic Liquids

Free radical polymerization of acrylonitrile (AN) in ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 2,2;m1-azobisisobutyronitrile (AIBN) as initiator was investigated. Early investigations on polymerizations using ionic liquids indicate that they serve as especially good solvents to achieve high molecular weight polymers. Free radical polymerizations result in higher molecular weight polymers, for ionic liquids have low chain transfer constants and act to stabilize the active radical during the process of polymerization. The thermal stability of polymers synthesized in ionic liquids have be improved obviously than that in traditional solvents.     

Effect of water and organic solvents on the ionic dissociation of ionic liquids

The effect of water and several organic solvents on the density, viscosity, and conductivity of ionic liquids (ILs) 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]), 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), and 1-n-butyl-3-methylimidazolium trifluoroacetate ([bmim][CF3CO2]) was studied at 298.15 K in wide composition ranges. The density, viscosity, and conductivity of the three neat ILs were also determined at various temperatures. Upon the basis of the molar conductivity of the mixtures and that of the neat ILs of the same viscosity, the degree of dissociation of ILs in the solutions was investigated. It can be deduced that the organic solvents enhance the ionic association of the ILs, the effect depending on the solvent dielectric constant, while water promotes dissociation significantly due to its high dielectric constant and its ability to form strong hydrogen bonds with the anions of the ILs.     

Nucleophilicity in ionic liquids. 3. Anion effects on halide nucleophilicity in a series of 1-butyl-3-methylimidazolium ionic liquids

We have continued the study of halide nucleophilicity in ionic liquids, concentrating on the effect of changing the anion ([BF(4)](-), [PF(6)](-), [SbF(6)](-), [OTf](-), and [N(Tf)(2)](-)) when the cation is [bmim](+) (where bmim = 1-butyl-3-methylimidazolium). It was found that the nucleophilicities of all the halides were lower in all of the ionic liquids than in dichloromethane. Changing the anion affected the order of halide nucleophilicity, e.g., in [bmim][BF(4)] the order of nucleophilicity was Cl(-)>Br(-)>I(-) while in [bmim][N(Tf)(2)] the order was Cl(-)相似文献   

Capillary zone electrophoresis of proteins applying ionic liquids for dynamic coating and as background electrolyte component

The use of ionic liquids in capillary electrophoresis, either as coating material or as components of the background electrolyte needs systematic standardization to set up optimal conditions. Excellent separation of the proteins was achieved using 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF₄]) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) ionic liquids using the properly made ionic-liquid–water binary mixtures for the experiments. The binary mixture has a distinctly stable and well perceptible low pH, which depends on the concentration of the ionic liquid, and on the preparation time of the mixture. Optimal conditions for the electrophoretic separation were obtained upon a multivariate analysis of the experimental parameters (applied voltage, migration time, concentration, and type of the ionic liquid). The standardized condition provides a low electroendosmotic flow toward the anode, which, however, did not hinder the proteins to migrate toward the cathode. The migration of cytochrome c, lysozyme, myoglobin, trypsin, and apo-transferrin at a pH around 2, far below the isoelectric points of the proteins, showed RSD values of the migration times less than 7.5% and less than 6.5% when using [emim][BF₄] or [bmim][BF₄], respectively, either in run-to-run or day-to-day experiments. The determination of the extent of the EOF is not possible with the commonly used EOF markers, due to interaction with the ionic-liquid constituents. The interaction of the ionic liquids with the proteins influences the migration order in zone electrophoresis. This method has been applied successfully for the analyses of real biological samples such as proteins from egg whites and human tears.     

Rotational dynamics of water and benzene controlled by anion field in ionic liquids: 1-butyl-3-methylimidazolium chloride and hexafluorophosphate

The rotational correlation time (tau(2R)) is determined for D(2)O (polar) and C(6)D(6) (apolar) in 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) and hexafluorophosphate ([bmim][PF(6)]) by measuring (2)H (D) nuclear magnetic resonance spin-lattice relaxation time (T(1)) in the temperature range from -20 to 110 degrees C. The tau(2R) ratio of water to benzene (tau(WB)) was used as a measure of solute-solvent attraction. tau(WB) is 0.73 and 0.52 in [bmim][Cl] and [bmim][PF(6)], respectively, whereas the molecular volume ratio is as small as 0.11. The slowdown of the water dynamics compared to the benzene dynamics in ionic liquids is interpreted by the Coulombic attractive interaction between the polar water molecule and the anion. As for the anion effect, the rotational dynamics of water solvated by Cl(-) is slower than that solvated by PF(6) (-), whereas the rotational dynamics of benzene is similar in the two ionic liquids. This is interpreted as an indication of the stronger solvation by the anion with a larger surface charge density. The slowdown of the water dynamics via Coulombic solvation is actually significant only at water concentrations lower than approximately 9 mol dm(-3) at room temperature, and it is indistinguishable at temperatures above approximately 100 degrees C. The quadrupolar coupling constants determined for D(2)O and C(6)D(6) in the ionic liquids were smaller by a factor of 2-3 than those in the pure liquid state.     

Quantitative High Performance Liquid Chromatography Determination of Alkanolamines in Ionic Liquid Absorbents

The development of modern absorption media suitable for CO₂ scrubbing, such as ionic liquids and their mixtures, requires appropriate analytical protocols. In this paper, the application of high-performance liquid chromatography to the determination of alkanolamine at various concentrations in ionic liquid solutions was investigated. Both hydrophilic and hydrophobic commercial ionic liquids, such as 1-butyl-3-methylimidazolium acetate [bmim][OAc], 1-ethyl-3-methylimidazolium octylsulfate [emim][OcSO₄], and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [bmim][NTf₂], were studied in this paper and different sample preparation procedures were used for each class of solvent. A simple extraction step was necessary prior to HPLC analysis for hydrophobic ionic liquids. This step was performed using five times more 0.05 M KH₂PO₄ than needed for the ionic liquid sample. Hydrophilic ionic liquid solutions could be analyzed after diluting the sample with water. The general procedure involved separation at room temperature using a cation-exchange HPLC with 0.05 M KH₂PO₄ as the mobile phase and refractometric detection without derivatizing the amines. The influence of the temperature and mobile phase composition on alkanolamine retention was investigated. The relationship between the peak area and alkanolamine concentration was linear over 3 orders of magnitude (2–200 nmol). The detection limit (LOD) for monoethanolamine (MEA) and diethanolamine (DEA) was 1.5 and 2 nmol, respectively. For hydrophobic ionic liquids, which require extraction, it was possible to analyze a 0.004% MEA solution. The quantity of the sample required for analysis was 0.1 g, and the analysis time did not exceed 20 minutes.     

The effect of hydrogen bonding on allylic alkylation and isomerization reactions in ionic liquids

Neutral allylic alkylation reactions, in which a base is generated in situ and which hence require no external bases, can significantly be retarded when carried out in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]). Evidence suggests that the base or base precursor enters into hydrogen bonding with the imidazolium cation and is thus made less readily available for deprotonation of pre-nucleophiles. However, the reaction proceeds well in the presence of stronger bases that are capable of deprotonation. Whilst the phenomenon of hydrogen bonding in ionic liquids can be detrimental to reactions such as allylic alkylation, it can be exploited to suppress unwanted allylic isomerization.