Thermomorphic Behavior of the Ionic Liquids [C4mim][FeCl4] and [C12mim][FeCl4]

The iron‐containing ionic liquids 1‐butyl‐3‐methylimidazolium tetrachloroferrate(III) [C₄mim][FeCl₄] and 1‐dodecyl‐3‐methylimidazolium tetrachloroferrate(III) [C₁₂mim][FeCl₄] exhibit a thermally induced demixing with water (thermomorphism). The phase separation temperature varies with IL weight fraction in water and can be tuned between 100 °C and room temperature. The reversible lower critical solution temperature (LCST) is only observed at IL weight fractions below ca. 35 % in water. UV/Vis, IR, and Raman spectroscopy along with elemental analysis prove that the yellow‐brown liquid phase recovered after phase separation is the starting IL [C₄mim][FeCl₄] and [C₁₂mim][FeCl₄], respectively. Photometry and ICP‐OES show that about 40 % of iron remains in the water phase upon phase separation. Although the process is thus not very efficient at the moment, the current approach is the first example of an LCST behavior of a metal‐containing IL and therefore, although still inefficient, a prototype for catalyst removal or metal extraction.     

新型碱性离子液体催化酯交换合成生物柴油

两步法合成了吗啉阴离子型碱性离子液体1-丁基-3-甲基吗啉盐Im,经 ¹H-NMR和FT-IR分析确认了离子液体中间体的结构,并通过阴离子交换得到碱性离子液体,对该离子液体在酯交换制备生物柴油反应中的催化性能进行了研究。结果表明,该碱性离子液体Im具有较高的酯交换催化活性,在60 ℃、催化剂用量为3%、醇油物质的量比为6.5：1.0、反应2 h的条件下,产物脂肪酸甲酯（FAME）含量可达95.80%。而且该离子液体的催化稳定性较好,重复使用5次后仍有较高的催化活性。     

Reverse ATRP Process of Methacrylonitrile in [C4mim][PF6]

In this original experiment, an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim][PF₆]), was used as the reaction media for reverse atom transfer radical polymerization of methacrylonitrile (MAN) initiated by azobisisobutyronitrile (AIBN) with FeCl₃ and isophthalic acid (IA) as catalyst and ligand. The polymerization in [C₄mim][PF₆] proceeded in a well-controlled manner as evidenced by kinetic studies. Compared with the polymerization in N, N-dimethylformamide (DMF), the polymerization in [C₄mim][PF₆] not only showed better control of molecular weight and narrower molecular weight distribution but also provided more rapid reaction rate with the ratio of [MAN]:[AIBN]:[FeCl₃]:[IA] at 300:1:2:4. The block copolymer PMAN-b-PSt was obtained via a conventional ATRP process in [C₄mim][PF₆] by using the resulting PMAN as macroinitiator. [C₄mim][PF₆] and FeCl₃/IA could be easily recycled and reused and had no effect on the living nature of reverse atom transfer radical polymerization of MAN.     

Ionic Association of the Ionic Liquids [C4mim][BF4], [C4mim][PF6], and [Cnmim]Br in Molecular Solvents

Considering the ionic nature of ionic liquids (ILs), ionic association is expected to be essential in solutions of ILs and to have an important influence on their applications. Although numerous studies have been reported for the ionic association behavior of ILs in solution, quantitative results are quite scarce. Herein, the conductivities of the ILs [C_nmim]Br (n=4, 6, 8, 10, 12), [C₄mim][BF₄], and [C₄mim][PF₆] in various molecular solvents (water, methanol, 1‐propanol, 1‐pentanol, acetonitrile, and acetone) are determined at 298.15 K as a function of IL concentration. The conductance data are analyzed by the Lee–Wheaton conductivity equation in terms of the ionic association constant (K_A) and the limiting molar conductance (Λ_m⁰). Combined with the values for the Br^? anion reported in the literature, the limiting molar conductivities and the transference numbers of the cations and [BF₄]^? and [PF₆]^? anions are calculated in the molecular solvents. It is shown that the alkyl chain length of the cations and type of anion affect the ionic association constants and limiting molar conductivities of the ILs. For a given anion (Br^?), the Λ_m⁰ values decrease with increasing alkyl chain length of the cations in all the molecular solvents, whereas the K_A values of the ILs decrease in organic solvents but increase in water as the alkyl chain length of the cations increases. For the [C₄mim]⁺ cation, the limiting molar conductivities of the ILs decrease in the order Br^?>[BF₄]^?>[PF₆]^?, and their ionic association constants follow the order [BF₄]^?>[PF₆]^?>Br^? in water, acetone, and acetonitrile. Furthermore, and similar to the classical electrolytes, a linear relationship is observed between ln K_A of the ILs and the reciprocal of the dielectric constants of the molecular solvents. The ILs are solvated to a different extent by the molecular solvents, and ionic association is affected significantly by ionic solvation. This information is expected to be useful for the modulation of the IL conductance by the alkyl chain length of the cations, type of anion, and physical properties of the molecular solvents.     

离子液体1-丙基-3-甲基咪唑醋酸盐[C_3mim][OAc]蒸气压和蒸发焓的测定及极性预测

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1-甲基-3-乙基咪唑缬氨酸盐离子液体[C2mim][Val]的热化学

用中和法合成了氨基酸离子液体1-甲基-3-乙基咪唑缬氨酸盐([CB_2Bmim][Val]). 在298.15±0.01 K下, 利用恒温溶解反应热量计测定了不同含水量的[CB_2Bmim][Val]溶解成不同质量摩尔浓度溶液的溶解焓, ΔB_solBHB_mB (w), 借助标准加入法(SAM)和Archer方法得到了无水离子液体[CB_2Bmim][Val]的标准摩尔溶解焓, . 利用RB-II型精密转动弹热量计测定了该离子液体的燃烧热, 计算了其标准摩尔燃烧焓 和标准摩尔生成焓 |并结合该离子液体的标准摩尔溶解焓和乙基咪唑阳离子[CB_2Bmim]^＋在水溶液中的标准摩尔生成焓, 计算了[Val]P^－离子在水溶液中的标准摩尔生成焓. 利用RD496-III型热导式微量热量计测定了不同质量摩尔浓度[CB_2Bmim][Val]水溶液的稀释焓, 根据扩展的Debye-Hückel方程计算得到的相对表观摩尔焓P^φPL和根据Pitzer离子相互作用模型的计算值在实验误差范围内很好一致.     

离子液体[C2mim][GaCl4]的溶解热研究

在干燥氩气氛下, 用等摩尔的高纯无水GaCl3和[C2mim][Cl](氯化1-甲基-3-乙基咪唑)直接搅拌混合, 制备了淡黄色透明的的离子液体[C2mim][GaCl4] (1-ethyl-3-methylimidazolium chlorogallate) . 在298.15 K下, 利用具有恒温环境的溶解反应热量计, 测定了这种离子液体的不同浓度摩尔溶解焓 . 针对[C2mim][GaCl4]溶解于水后即分解的特点, 在Pitzer电解质溶液理论基础上, 提出了确定这种离子液体标准摩尔溶解焓的新方法, 得到了[C2mim][GaCl4]在水中的标准摩尔溶解焓, ＝－132 kJ•mol－1, 以及Pitzer焓参数组合: ＝－0.1373076和 ＝0.3484209. 借助热力学循环和Glasser离子液体晶格能理论, 用Ga3＋, Cl－和[C2mim]—的离子水化焓数据以及本文得到的[C2mim][GaCl4]标准摩尔溶解焓, 估算了配离子4Cl－(g)解离成Ga3＋(g)和4Cl－(g)的解离焓ΔHdis([GaCl4]-)≈5855 kJ•mol－1. 这个结果揭示了离子液体[C2mim][GaCl4]的标准摩尔溶解焓绝对值并不很大的原因, 即是很大的离子水化焓被很大的[GaCl4]－(g)的解离焓相互抵消了.     

[Bmim]FeCl_4离子液体的物理性质

研究了自制[Bmim]FeCl4离子液体的电导率、黏度与温度的关系,并与文献数据进行了对比.结果表明,采用落球法和旋转法都能准确地测量[Bmim]FeCl4离子液体的黏度;与Andrade方程相比,VTF方程能更好地拟合[Bmim]FeCl4离子液体的黏度和温度的关系,其相关系数达0.999 9.采用不同电导率仪测量的[Bmim]FeCl4离子液体的电导率有较大差别;相比Arrhenius方程而言,VTF方程能更好地拟合电导率与温度的关系;随着温度的变化,电导率与黏度的关系符合Walden规则,其相关系数达到0.99以上.     

The surface tension,density and refractive index of amino acid ionic liquids: [C3mim][Gly] and [C4mim][Gly]

The amino acid ionic liquids (AAILs) [C₃mim][Gly] (1-propyl-3-methylimidazolium glycine) and [C₄mim][Gly] (1-butyl-3-methylimidazolium glycine) have been prepared by the neutralization method and characterized by ¹H NMR spectroscopy and differential scanning calorimetry (DSC). The values of their density, surface tension and refractive index were measured at different temperatures. Since the AAILs can form strong hydrogen bonds with water, small amounts of water are difficult to remove from the AAILs by common methods. In order to eliminate the effect of the impurity as water, the standard addition method (SAM) was applied to these measurements. The values of thermal expansion coefficients, α, surface excess energy, E_a, surface excess entropy, S_a, and molar refraction, R_m, for the AAILs were determined.     

离子液体[bmim]PTSA的微波合成

近年来,随着绿色化学的兴起,离子液体作为一种新型的绿色溶剂已成为国内外科研工作者的研究热点之一.离子液体是由有机阳离子和无机阴离子组成的盐,可以根据需要控制阴阳离子的组成和结构,设计合成出不同特性的离子液体[1].     

A new type of microemulsion containing task-special ionic liquid [NH2ebim][BF4]

The formation of microemulsions in the presence of cyclohexane, Triton X-100, n-butanol, water, and task-special ionic liquid (TSIL) (1-2-aminoethyl-3-butylimidazolium tetrafluoroborate) was studied at 25°C. The phase behavior of this ternary system was investigated. Three subregions (namely, water-in-oil phase, bicontinuous phase, and oil-in-water phase) were identified in the single-phase region by dynamic light scattering (DLS) technique and electrical conductivity measurement. Microstructures of microemulsions with different water contents have been predicted by using dissipative particle dynamics (DPD) simulation. It was found that the DPD simulations successfully reproduce the experimental results in the article. The location of TSIL in the microemulsions was predicted by DPD simulation further. The result indicates that TSIL is more easy to locate in the surfactant and cosurfactant layer and has amphiphilicity, which provides us new insights into the potential applications of TSIL-based microemulsions in separation and new nano-scale material preparation because of the interaction of TSIL with some special components at the interface of oil and water.     

Microwave-accelerated Claisen rearrangement in bicyclic imidazolium [b-3C-im][NTf2] ionic liquid

With microwaves, a chemically stable ionic liquid [b-3C-im][NTf₂] recently developed in our laboratory was used as solvent and successfully applied to accelerate Claisen rearrangement reactions at high temperatures. In the presence of Lewis acid MgCl₂, these thermal rearrangements could be achieved in similar reaction times but at lower temperature. For the microwaved reactions studied in this work, without scarifying isolated yields, the reaction times were significantly reduced from hours (by conventional heating) to ≤3 min. Our result also demonstrated that [b-3C-im][NTf₂] ionic liquid was a useful solvent substitute and could be recycled multiple times for the studied rearrangement reaction at elevated temperatures.     

[C_2mim][Ala]丙氨酸离子液体水溶液粘滞流动的活化参数

在288.15-328.15 K温度范围内,测量了不同浓度的氨基酸离子液体[C_2mim][Ala]水溶液的密度和粘度,根据J ones-Dole方程得到了较大正值的粘度B系数并且dB/dT0。借助Feakins理论,计算了溶质对溶液粘滞流动活化自由能贡献Δμ_2~(≠0),根据Δμ_2~(≠0)随温度的线性变化,进而得到流动活化熵ΔS_2~(≠0)和活化焓ΔH_2~(≠0);在E yring液体粘度的过渡态理论基础上,提出了预测离子液体[C_2mim][Ala]水溶液粘度的半经验新方法,其预测值与相应的实验值很好的一致。     

丙氨酸离子液体[C4mim][Ala]的热化学性质

在298.15 K下利用恒温环境溶解热量计测定了一系列含有已知微量水的1-丁基-3-甲基咪唑丙氨酸盐([C₄mim][Ala])离子液体(IL)不同浓度样品的摩尔溶解焓. 借助Debye-Hückel极限项, 用外推法确定了不同含水量的[C₄mim][Ala]样品的标准摩尔溶解焓[Δ_sH_m⁰(wc)]. 随着样品中水含量的增加, Δ_sH_m⁰(wc)的绝对值下降, 将Δ_sH_m⁰(wc)对含水量作图得到很好的直线, 其截距Δ_sH_m⁰(pure IL)=-60.74 kJ/mol, 可看作是不含水的[C₄mim][Ala]标准摩尔溶解焓的估算值. 利用精密氧弹热量计测定了[C₄mim][Ala]的燃烧热, 计算得到其标准摩尔生成焓Δ_fH_m⁰=(-675±11) kJ/mol.     

Estimation of physico-chemical properties of ionic liquid [C7mim][BF4]

Ionic liquid (IL) [C₇mim][BF₄] (1-heptyl-3-methyl-imidazolium tetrafluoroborate) was prepared and characterized. The density and surface tension of the IL were determined in the temperature range of 293.15–343.15 K. In terms of Glasser's theory, the standard molar entropy and lattice energy of the IL were estimated. Using Kabo's method, the molar enthalpy of vaporization of the IL, Δ_l^gH_m⁰ (298 K), was estimated. According to the interstice model, the thermal expansion coefficient of IL, α, was calculated and in comparison with experimental value, they are within one order of magnitude.     

Increased enantioselectivity and remarkable acceleration of lipase-catalyzed transesterification by using an imidazolium PEG-alkyl sulfate ionic liquid

Several types of imidazolium salt ionic liquids were prepared derived from poly(oxyethylene)alkyl sulfate and used as an additive or coating material for lipase-catalyzed transesterification in an organic solvent. A remarkably increased enantioselectivity was obtained when the salt was added at 3-10 mol % versus substrate in the Burkholderia cepacia lipase (lipase PS-C)-catalyzed transesterification of 1-phenylethanol by using vinyl acetate in diisopropyl ether or a hexane solvent system. In particular, a remarkable acceleration was accomplished by the ionic liquid coating with lipase PS in an iPr(2)O solvent system while maintaining excellent enantioselectivity; it reached approximately 500- to 1000-fold acceleration for some substrates with excellent enantioselectivity. A similar acceleration was also observed for IL 1-coated Candida rugosa lipase. MALDI-TOF mass spectrometry experiments of the ionic-liquid-coated lipase PS suggest that ionic liquid binds with lipase protein.     

Study on physicochemical properties of ionic liquids based on alanine [Cnmim][Ala] (N=2,3,4,5,6)

According to Fukumoto's method, a new series of ionic liquids (ILs) based on alanine, [Cnmim][Ala] ( n=2,3,4,5,6), which comprise 1-alkyl-3-methylimidazolium cation ([Cnmim](+)) and alanine anions ([Ala] (-)), were prepared and characterized. In terms of standard addition method, the density and surface tension of amino acid ILs [Cnmim][Ala] (1-alkyl-3-methylimidazolium alpha-aminopropionic acid salt) were measured in the temperature range 293.15-343.15+/-0.05 K. The volume and surface properties of the ILs [Cnmim][Ala] were discussed. A new method of determining parachor of ionic compound was proposed and was applied to estimate the physicochemical properties of amino acid ionic liquids (AAILs): molecular volume, surface tension, molar enthalpy of vaporization, and thermal expansion coefficient. In comparison with Deetlefs's method of using neutral parachor contribution, the method proposed in this work makes smaller error in estimating properties of AAILs.