Effect of Hydroxyl Groups in a Cation Structure on the Properties of Ionic Liquids

Two series of imidazolium ionic liquids with the bis(trifluoromethylsulfonyl)imide anion were synthesized, which differ by the presence of a hydroxyl group at the ω-position of the alkyl substituent in the cation structure (n_C = 2–8). The properties of the liquids were studied by DSC, TGA, and IR and NMR spectroscopy. Their thermal stability was studied, and the melting points, viscosity, and volatility in vacuum were measured. The effect of OH groups in the structure of the ionic liquid on its properties was evaluated.     

The synthesis of an aryl alkyl ionic liquid and its application in catalyzing Suzuki-Miyaura coupling reaction

An aryl alkyl ionic liquids with a tertiary amino group (N(CH₃)₂) in the cation were synthesized. As a ligand, the synthesized ionic liquids can coordinate with palladium to form N-heterocyclic carbene (NHC)-Pd complex which exhibited high efficiency in catalyzing Suzuki-Miyaura coupling reaction.     

以N为中心的阴离子离子液体的合成、表征及应用

首次通过不同阴离子的钾盐和不同的季铵化的咪唑,吡咯溴盐/氯盐进行离子交换,合成了一系列含氰基官能团的阴离子功能化离子液体。通过红外、核磁共振、质谱对离子液体的结构进行表征;通过TGA对离子液体的热稳定性进行测定,结果发现功能化离子液体具有良好的热稳定性,其分解温度在224-289℃范围内。将功能化离子液体[EMIm][N(CN)COC2H5]作为配体应用于无膦配体的Suzuki偶联反应,发现在反应中加入功能化离子液体[EMIm][N(CN)COC2H5]可以使反应收率提高10-20%。     

Dicationic polysiloxane ionic liquids

Dicationic ionic liquids with bis(trifluoromethylsulfonyl)imide anions and dimethylimidazolic moieties linked by the polymeric siloxane chain in the cation structure have been synthesized. Thermal stability of the compounds synthesised was studied by TGA; glass transition temperatures, viscosities and volatility in vacuo were measured. Applicability of these ionic liquids as heat carriers under high dynamic vacuum conditions is shown.     

Porous texture of silica aerogels made with ionic liquids as gelation catalysts

The effect of four ionic liquids on the porous texture of silica aerogels synthesized from mixed tetramethoxysilane and methyltrimethoxysilane and dried by the CO₂ supercritical method, was studied. Two of these ionic liquids were composed of BF₄ ⁻ anions while the other two included Cl⁻ anions. The synthesis of gels from ionic liquids did not require another acidic catalyst for silica hydrolysis, nor a basic catalyst for silica condensation. These aerogels were compared with traditional aerogels made according to a double step catalysis, which first involved hydrolysis with HCl followed by condensation with pH 9 Tris HCl buffer. Gel mass analysis and thermogravimetric data showed that, when the initial molar of ionic liquid to Si was 1.58, only ~2% (by mass) of the initial ionic liquids consisting of BF₄ ⁻ anions and ~10% (by mass) of ionic liquids containing Cl⁻ anions, remained in the aerogels after supercritical drying. Moreover, X-ray diffraction confirmed that in ionic liquids based on BF₄ ⁻ anions, evaporation of the volatile components before supercritical CO₂ drying led to the formation of regularly ordered mesopores.     

Preparation and Characterization of a Novel Benzimidazolium Bronsted Acid Ionic Liquid and Its Application in the Synthesis of Arylic Esters

A novel Brφnsted acid task specific ionic liquid 1-ethylbenzimidazolium tetrafluoroborate （[Hebim]BF4） with functional benzimidazolium cation was synthesized and characterized by ^1H NMR, IR, MS spectra and elemental analysis. This novel ionic liquid was successfully used as dual solvent-catalyst for the synthesis of arylic esters. Higher yields were obtained in the presence of [Hebim]BF4 in comparison with other imidazolium ionic liquids because of the good solubility of the aromatic alcohols and aromatic carboxylic acids in [Hebim]BF4. The product could be separated conveniently from the reaction system, and the ionic liquid could be easily reused after removal of water under vacuum. After 10 times reuse, the selectivity of the ester was still 100%.     

含氰基基团的以C为中心的不对称阴离子离子液体的合成、表征及应用

首次通过不对称阴离子的钠盐/钾盐和不同的季胺化的咪唑,吡咯溴盐/氯盐进行离子交换,合成了一系列含氰基官能团的不对称阴离子功能化离子液体。通过红外、核磁共振、质谱和元素分析对离子液体的结构进行表征;通过TGA对离子液体的热稳定性进行测定,结果发现不对称功能化离子液体具有良好的热稳定性,其分解温度在219-319℃范围内。将功能化离子液体[Bmim][C(CN)2COCH3]作为弱配体应用于模型的Suzuki偶联反应,发现在反应中加入功能化离子液体[Bmim][C(CN)2COCH3]可以使反应收率提高10-15%。     

Mandelate and prolinate ionic liquids: synthesis, characterization, catalytic and biological activity

A group of quaternary ammonium mandelates and l-prolinates, as ionic liquids, were synthesized and characterized. The prepared salts were soluble in water and showed high surface activity. The described synthesis of l-prolinate was simple and the obtained ionic liquid contained a chiral anion. l-Prolinate in CH₂Cl₂ was employed for the asymmetric Michael addition of a ketone to nitrostyrene. A yield of 60%, enantioselectivity (upto 50% ee), and good diastereoselectivity (syn/anti ratio of up to 90:10) were obtained for the asymmetric addition of cyclohexanone. These novel ionic liquids proved to be very effective anti-microbial and anti-fungal agents, especially didecyldimethylammonium l-prolinate. Additionally, it was found that phytotoxicity can be a useful tool in assessing the optical forms of ionic liquids.     

Study of new synthesized ferrocenyl ionic liquids in oxidative esterification reaction

In this work, novel ferrocene-based ionic liquids, 1-(ferrocenylbutyl)-4-(3-methylimidazolium) Azide and 1-(ferrocenylbutyl)-4-(3-methylimidazolium) Tetrafluoroborate, were synthesized and utilized in the oxidation esterification reaction of aldehydes in the present of different reagents such as NaN₃, (K₂CO₃ and NCS), (KI and KCN), (I₂ and K₂CO₃), (KMnO₄). The results were compared with that of [BMIM][X] (X?Cl, BF₄) under the same conditions. As expected, ferrocene-based ionic liquids showed better results; It seems, iron nuclear may play a similar role such as iron catalysts in these novel ionic liquids and can facilitated the oxidation esterification reaction with improve the yield and decrease the reaction time.     

Synthesis and dissolving power of 1-Alkyl-3-methylpyridinium-based ionic liquids

1-Alkyl-3-methylpyridinium-based ionic liquids with substituents from C₂ to C₁₀ and anions Cl^? and Br^? were synthesized, and their dissolving power toward the cellulose was investigated. The results of quantum-chemical calculations of molecules of ionic liquids are presented.     

酸功能化-温控型三元杂多酸离子液体的合成、表征及其酯催化性能

采用酸化-乙醚萃取法制备了不同钒取代数目的 Keggin结构的磷钨钒杂多酸,并进一步通过离子交换法合成了磺酸功能化的杂多酸离子液体催化剂,采用核磁、元素分析、红外、紫外、X射线衍射、热重-差示扫描、电位滴定等分析手段对所得样品进行了表征,考察了所得样品对氯乙酸和正戊醇的酯化反应性能和重复使用性能。结果表明,所制备的杂多酸离子液体是一种具有温度响应特性的无定型结构化合物,仍保留Keggin结构和较高的酸强度,该催化剂在反应温度下与反应物形成一相,而反应结束温度降低后,催化剂和产物又形成两相,通过简单的倾倒法就可以快速分离催化剂和反应产物。与杂多酸以及未磺酸化的杂多酸离子液体相比,磺酸功能化的杂多酸离子液体具有更高的酯催化活性。在优化的反应条件下,[PyPS]4PW11VO40(PyPS为1-(3-磺酸基)丙基吡啶)对氯乙酸的转化率可达到97.6%,重复使用4次后转化率为91.9%,而催化剂的结构未有明显变化。     

Synthesis and Characterization of Task‐Specific Ionic Liquids Possessing Two Brönsted Acid Sites

Abstract

Task‐specific ionic liquids possessing two Brönsted acid sites with –COOH, HSO^? ₄, or H₂PO^? ₄ groups have been designed, synthesized, and characterized. Under mild conditions and without any additional organic solvent, the esterification of isopropanol by chloroacetic acid could be carried out in these new task‐specific ionic liquids. In comparison with most of acidic ionic liquids in current use, these ionic liquids are halogen free and more environmentally benign as media and catalysts.     

Adding magnetic ionic liquid monomers to the emulsion polymerization tool‐box: Towards polymer latexes and coatings with new properties

Magnetic ionic liquid monomers were synthesized and then polymerized to get magnetic polymer latexes and films. First, a series of 1‐vinyl‐3‐dodecyl‐imidazolium monomers having metal halides counter‐anions such as FeCl₃Br^?, CoCl₂Br^?, and MnCl₂Br^? were synthesized. These ionic liquid monomers were first homopolymerized to lead to magnetic poly(ionic liquids) and characterized. Secondly, magnetic latexes were synthesized by using the magnetic ionic liquids as surfmers (surfactant + monomer) in the emulsion polymerization of methyl methacrylate/n‐butyl acrylate. It was found that the powders obtained by freeze‐drying the latexes presented a paramagnetic behavior with weak antiferromagnetic interactions between the adjacent metal ions. Although the ratio of magnetic ionic liquid/monomer was only 2% these poly(methyl methacrylate‐co‐butyl acrylate) powders and latexes responded to a magnetic field due to the surfmer paramagnetic nature. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1145–1152     

Synthesis of methyl orange using ionic liquids

Two ionic liquids were synthesized, each system consisting of the 1-hexyl-3-methylimidazolium ion ([hmim]⁺) as the cation and either hexafluorophosphate ([PF₆]⁻), or perchlorate ([ClO₄]⁻) as the anions. This study involves the synthesis of methyl orange (4-[[(4-dimethylamino)phenyl]-azo] benzene sulfonic acid sodium salt) using the ionic liquids as replacement solvents for the reaction. The advantage of using ionic liquids as substitutes for organic solvents includes: recyclable/reclaimable solvents, stabilization of intermediates and higher product yields. The 1-hexyl-3-methylimidazolium derivatives can be used for syntheses conducted at low temperatures and are less toxic than typical organic solvents.     

Acidic Ionic Liquids as Efficient and Environmentally Benign Medium for the Synthesis of 2-Phenylbenzimidazole

2‐Substituted benzimidazoles have been synthesized in excellent yields under solvent‐free conditions using a series of acidic ionic liquids as catalysts. The results indicate that SO₃H‐functionalized ionic liquids show higher catalytic activities than other acidic ionic liquids. The effects of reaction conditions such as the amounts of ionic liquids, the ratio of reactants were investigated. A Hammett method was used to determine the acidity order of these ionic liquids and the results were found to be relevant to the catalytic activities observed in the synthesis reaction. Besides, the reaction mechanism was stimulated using DFT method.     

Exploring Sustainable Rocket Fuels: [Imidazolyl−Amine−BH2]+‐Cation‐Based Ionic Liquids as Replacements for Toxic Hydrazine Derivatives

The application of hypergolic ionic liquids as propellant fuels is a newly emerging area in the fields of chemistry and propulsion science. Herein, a new class of [imidazolyl?amine?BH₂]⁺‐cation‐based ionic liquids, which included fuel‐rich anions, such as dicyanamide (N(CN)₂^?) and cyanoborohydride (BH₃CN^?) anions, were synthesized and characterized. As expected, all of the ionic liquids exhibited spontaneous combustion upon contact with the oxidizer 100 % HNO₃. The densities of these ionic liquids varied from 0.99–1.12 g cm^?3, and the heats of formation, predicted based on Gaussian 09 calculations, were between ?707.7 and 241.8 kJ mol^?1. Among them, the salt of compound 5 , that is, (1‐allyl‐1H‐imidazole‐3‐yl)?(trimethylamine)?dihydroboronium dicyanamide, exhibited the lowest viscosity (168 MPa s), good thermal properties (T_gT_d>130 °C), and the shortest ignition‐delay time (18 ms) with 100 % HNO₃. These ionic fuels, as “green” replacements for toxic hydrazine‐derivatives, may have potential applications as bipropellant formulations.     

离子液体中酮肟O-烷基化反应的研究

以[Bmim]PF6,[Bmim]BF4,[Bmim]OH为介质,以NaOH为缚酸剂,由酮肟与卤烷、硫酸酯等烷基化剂在20～40℃反应1～2h,以52%～94%的收率制备了酮肟醚衍生物,产物结构经1HNMR,GC-MS表征.结果表明,该方法简便易操作,所用离子液体对环境友好,并可循环使用.     

Design of guanidinium ionic liquid based microwave‐assisted extraction for the efficient extraction of Praeruptorin A from Radix peucedani

A series of novel tetramethylguanidinium ionic liquids and hexaalkylguanidinium ionic liquids have been synthesized based on 1,1,3,3‐tetramethylguanidine. The structures of the ionic liquids were confirmed by ¹H NMR spectroscopy and mass spectrometry. A green guanidinium ionic liquid based microwave‐assisted extraction method has been developed with these guanidinium ionic liquids for the effective extraction of Praeruptorin A from Radix peucedani. After extraction, reversed‐phase high‐performance liquid chromatography with UV detection was employed for the analysis of Praeruptorin A. Several significant operating parameters were systematically optimized by single‐factor and L₉ (3⁴) orthogonal array experiments. The amount of Praeruptorin A extracted by [1,1,3,3‐tetramethylguanidine]CH₂CH(OH)COOH is the highest, reaching 11.05 ± 0.13 mg/g. Guanidinium ionic liquid based microwave‐assisted extraction presents unique advantages in Praeruptorin A extraction compared with guanidinium ionic liquid based maceration extraction, guanidinium ionic liquid based heat reflux extraction and guanidinium ionic liquid based ultrasound‐assisted extraction. The precision, stability, and repeatability of the process were investigated. The mechanisms of guanidinium ionic liquid based microwave‐assisted extraction were researched by scanning electron microscopy and IR spectroscopy. All the results show that guanidinium ionic liquid based microwave‐assisted extraction has a huge potential in the extraction of bioactive compounds from complex samples.     

Synthesis and Properties of Alkoxy‐ and Alkenyl‐Substituted Peralkylated Imidazolium Ionic Liquids

Novel peralkylated imidazolium ionic liquids bearing alkoxy and/or alkenyl side chains have been synthesized and studied. Different synthetic routes towards the imidazoles and the ionic liquids comprising bromide, iodide, methanesulfonate, bis(trifluoromethylsulfonyl)imide ([NTf₂]^?), and dicyanamide {[N(CN)₂]^?} as the anion were evaluated, and this led to a library of analogues, for which the melting points, viscosities, and electrochemical windows were determined. Incorporation of alkenyl moieties hindered solidification, except for cations with high symmetry. The alkoxy‐derivatized ionic liquids are often crystalline; however, room‐temperature ionic liquids (RTILs) were obtained with the weakly coordinating anions [NTf₂]^? and [N(CN)₂]^?. For the viscosities of the peralkylated RTILs, an opposite trend was found, that is, the alkoxy derivatives are less viscous than their alkenyl‐substituted analogues. Of the crystalline compounds, X‐ray diffraction data were recorded and related to their molecular properties. Upon alkoxy substitution, the electrochemical cathodic limit potential was found to be more positive, whereas the complete electrochemical window of the alkenyl‐substituted imidazolium salts was shifted to somewhat more positive potentials.     

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.