A simple and efficient thia-Michael addition to α, β-unsaturated ketones catalyzed by Yb(OTf)3 in [bmim][BF4]

Yb(OTf)₃ in an ionic liquid [bmim][BF₄] has been described as an efficient catalyst for the thia-Michael addition of thiols to α,β -unsaturated ketones to give β -aryl-β-mercapto ketones in 82–94% yield and the catalyst along with ionic liquid was recycled and reused.     

ARGET ATRP of acrylonitrile with ionic liquid as reaction medium and FeBr3/isophthalic acid as catalyst system

Atom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile with FeBr₃ and isophthalic acid (IA) as catalyst and ligand, ascorbic acid (VC) as reducing agent, and ethyl 2‐bromoisobutyrate as initiator was approached for the first time in the presence of air in 1‐dodecyl‐3‐methylimidazolium tetrafluoroborate ([C₁₂mim][BF₄]), 1‐octyl‐3‐methylimidazolium tetrafluoroborate ([C₈mim][BF₄]), and 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([C₄mim][BF₄]). The rate of polymerization in [C₁₂mim][BF₄] was considerably faster than in [C₈mim][BF₄] and [C₄mim][BF₄]. With an increase of VC concentration, both the monomer conversion and the molecular weight distribution showed a trend of increase. Polyacrylonitrile (PAN) with higher molecular weight at 166,250 and broader distribution at 1.34 was successfully prepared with PAN as macroinitiator via ARGET ATRP in [C₁₂mim][BF₄] in the presence of air. The resultant polyacrylonitrile fibers were obtained with the fineness at 1.15 dtex and the tenacity at 6.24 cN dtex^?1. Additionally, it was shown that [C₁₂mim][BF₄] could be recycled and reused after simple purification and had no effect on the living nature of polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

1‐Allyl‐3‐methylimidazolium halometallate ionic liquids as efficient catalysts for the glycolysis of poly(ethylene terephthalate)

Series of 1‐allyl‐3‐methylimidazolium halometallate ionic liquids (ILs) were synthesized and used to degrade poly(ethylene terephthalate) (PET) as catalysts in the solvent of ethylene glycol. One important feature of these new IL catalysts is that most of them, especially [amim][CoCl₃] and [amim][ZnCl₃], exhibit higher catalytic activity under mild reaction condition, compared to the traditional catalysts [e.g., Zn(Ac)₂], the conventional IL catalysts (e.g., [bmim]Cl), Fe‐containing magnetic IL catalysts (e.g., [bmim][FeCl₄]), and metallic acetate IL catalysts (e.g., [Deim][Zn(OAc)₃]). For example, using [amim][ZnCl₃] as catalyst, the conversion of PET and the selectivity of bis(hydroxyethyl) terephthalate (BHET) reach up to 100% and 80.1%, respectively, under atmospheric pressure at 175°C for only 1.25 h. Another important feature is that BHET can be easily separated from the catalyst and has a high purity. Finally, based on the experimental phenomena, in ‐situ infrared spectra, and experimental results, the possible mechanism of degradation with synthesized IL is proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Physical and electrochemical properties of 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium iodide,and 1-butyl-3-methylimidazolium tetrafluoroborate

The density, viscosity, refractive index, heat capacity, heat of dilution, ionic conductivity, and electrochemical stability of 1-butyl-3-methylimidazolium bromide ([bmim][Br]), 1-butyl-3-methylimidazolium iodide ([bmim][I]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) were measured at room temperature or over a temperature range of 293.2 to 323.2 K. The density and refractive index values of [bmim][I] appeared to be the highest among three ionic liquids (ILs). However, the experimental viscosity values of [bmim][Br] were higher than those of [bmim][BF₄], while the heat capacities and heats of dilution of [bmim][BF₄] were higher than those of [bmim][Br]. The cyclic voltammogram of [bmim][br] and [bmim][BF₄] indicated electrochemical windows in the stability range from 2.7 V of [bmim][[Br] to 4.7 V of [bmim][BF₄].     

Mannich reaction catalyzed by carboxyl-functionalized ionic liquid in aqueous media

Three-component Mannich reactions of aromatic aldehydes, anilines and acetophenone were efficiently catalyzed by a recyclable carboxyl-functionalized ionic liquid ([cmmim][BF₄]) in aqueous [bmim][BF₄] under mild conditions. Twelve β-aminoketones were successfully synthesized in high yields and the catalyst can be recycled at least 6 times without significant loss of activity.     

Critical properties and acentric factors of ionic liquids

Since most ionic liquids (ILs) decompose before reaching their critical state, the experimental measurement of their critical properties are not possible. In this study, the critical temperatures, critical pressures and acentric factors of ten commonly investigated ILs were determined by making an optimum fit of the calculated vapor-liquid equilibrium data of binary mixtures of CO₂+IL to the experimental values found in literature. For this purpose, the Peng-Robinson equation of state (PR EoS) and the differential evolution optimization method were used. The ILs considered were 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][PF₆]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([emim][Tf₂N]), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][Tf₂N]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][BF₄]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF₆]), 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([hmim][Tf₂N]), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF₄]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF₆]). To evaluate the ability of the determined parameters in predicting the phase behavior of systems other than the systems that were used for parameter optimization, both sets of parameters obtained in this work and that of Valderrama et al. were used to predict bubble-point pressures of CHF₃+[bmim][PF₆] (by using the PR EoS and the Soave-Redlich-Kwong equation of state. The bubble-point pressures of CO₂+IL systems optimized in this study by the PR EoS were also determined using the Soave-Redlich-Kwong equation of state (SRK EoS). In addition, liquid densities of pure ILs were predicted using a generalized correlation proposed by Valderrama and Abu-Shark. In all cases, the various predicted properties of these ten ILs, were in better agreement with the experimental data, using the critical properties and acentric factor obtained in this study, compared to the values suggested by Valderrama et al.     

Catalytic Activity of Pd(II) Complexes with Triphenylphosphito Ligands in the Sonogashira Reaction in Ionic Liquid Media

The reactivity of palladacycle dimeric complexes with substituted triarylphosphito ligands P(OR)₃ (R = Ph, m-MeC₆H₄, o-MeC₆H₄, C₆H₃-2,4-tBu₂) as well as their non-orthometallated analogues PdCl₂[P(OR)₃]₂ was tested in a copper-free Sonogashira reaction with iodobenzene and phenylacetylene as substrates and imidazolium ionic liquids as the reaction medium. The ionic liquids [bmim][PF₆], [bmim][BF₄] and [emim][SO₄Et] were chosen. The palladium complexes studied showed high activity, and the yield of diphenylacetylene ranged from 31 to 98% in 1 h. The best results were obtained in [bmim][PF₆] for PdCl₂[P(O-m-MeC₆H₄)₃]₂ (84%) and for orthopalladated dimer with the same phosphite (98%).     

Ionic Liquid, 1‐n‐Butyl‐3‐methylimidazolium Bis(trifluoromethanesulfonyl)imide,Resulted in the First Catalyst‐Free Aminohalogenation of Electron‐Deficient Alkenes

The 2‐Ns‐based aminohalogenation of α,β‐unsaturated ketones has been achieved in an ionic liquid, 1‐n‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide {[bmim][N(SO₂CF₃)₂]}. [Bmim][N(SO₂CF₃)₂] was found to be superior not only to classical organic solvents but also to its counterpart, [bmim][BF₄], which was proven to be successful in the TsNCl₂‐based aminohalogenation but failed to give any product for this reaction. The present process takes the advantage of 2‐NsNCl₂ as the stable nitrogen/halogen source in a one‐pot operation without the use of any metal catalysts, it is convenient to perform without special protection of inert gases. Eight examples were examined with good to excellent stereoselectivity (1:5 to one isomer) and modest to good chemical yields (53–72 %).     

Brønsted acid-free controlled polymerization of tetrahydrofuran catalyzed by recyclable rare earth triflates in the presence of epoxides

We report a series of novel, highly efficient, hydrolytically stable and recyclable Lewis acid rare earth triflate catalysts for the living/controlled bulk ring-opening polymerization (ROP) of tetrahydrofuran (THF) in the presence of epoxides. The rare earth triflates [RE(OTf)₃] include that of Sc, Y, La, Nd, Dy and Lu. Epoxides include propylene oxide (PO), cyclohexene oxide (CHO) or styrene oxide (SO). Especially RE(OTf)₃/PO shows high activities, producing PTHF with up to 62 percent conversion and relatively narrow molecular weight distributions (MWDs) (as low as 1.14). Molecular weights (MWs) can be readily controlled from 1.7 to 56.1 kDa by changing monomer to catalyst molar ratios. The Sc(OTf)₃/PO catalyst gives an α,ω-dihydroxyl telechelic PTHF with MWs close to calculated values and MWDs below 1.2. The rare earth catalysts are easily recovered by simple water extractions. For instance, Sc(OTf)₃ can be used at least six times without an obvious decrease of catalytic activity. A polymerization mechanism involving the first two propagation steps of the alkyltetrahydrofuranium cation is proposed to account for the induction periods observed.     

Reverse atom transfer radical polymerization of methyl methacrylate in imidazolium ionic liquids

Reverse atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) employing 2,2-azobisisobutyronitrile (AIBN)/CuCl₂/bipyridine(bipy) as the initiating system was approached at 80 °C in two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) and 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C₁₂mim][BF₄]), respectively. The polymerization in [C₁₂mim][BF₄] proceeded in a well-controlled manner as evidenced by kinetic studies, end group analysis, chain extension, and block copolymerization results, but not in [C₄mim][BF₄] presumably due to poor solubility of PMMA in it. The kinetic study of reverse ATRP of MMA in recycled [C₁₂mim][BF₄] suggested that this ionic liquid could be re-used as reaction solvent after simple purification, without affecting the living nature of polymerization.     

Epoxidation of alkenes with hydrogen peroxide catalyzed by 1-methyl-3-butylimidazoliumdecatungstate in ionic liquid

The epoxidation of alkenes with hydrogen peroxide catalyzed by a new tungsten catalyst 1-methyl-3-butylimidazoliumdecatungstate in [bmim][BF₄] ionic liquid is described. The epoxides are obtained in high yield, catalyst can be recycled and the reaction conditions are simple and environmentally benign.     

Ionic Liquid Confined in Nafion: Toward Molecular‐Level Understanding

In this article, multiscale simulation methods were used to study structural and transport properties of Nafion–ionic liquid composite membranes that are novel proton conducting materials for fuel cells. Coarse‐grained model for 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]) ionic liquid was first developed in the framework of BMW‐MARTINI force field. Coarse‐grained simulation results of bulk [bmim][BF₄] ionic liquid show good agreement with all‐atom simulation results and experimental data. Nafion–[bmim][BF₄] composite membranes were then simulated using all‐atom and coarse‐grained models. Ionic liquid cluster formation inside Nafion was revealed by coarse‐grained simulations. Diffusion coefficients of both [bmim]⁺ cations and anions are reduced by one to two orders of magnitude depending on their concentrations in Nafion membrane. [Bmim]⁺ cations have faster self‐diffusion coefficient than anions, while this phenomenon is more pronounced when ionic liquids are confined in Nafion. This work provides molecular basis for understanding Nafion–ionic liquid composite membranes. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2630–2639, 2013     

Effect of ionic liquids on the structural,thermal, and in vitro degradation properties of poly(ε‐caprolactone) synthesized in the presence of Candida antarctica lipase B

The study provides detailed information on the differences in the structural, thermal and degradation properties of poly(ε‐caprolactone) synthesized in two different ionic liquids, 1‐butyl‐3‐methylimidazolium hexafluorophosphate [bmim][PF₆] and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide [bmim][NTf₂], regarding its further usage in the pharmaceutical field. The polymer structure confirms the presence of both linear polymer chains with end‐functional hydroxyl groups allowing covalent coupling of the therapeutic agents, and cyclic macromolecules, both affecting the degree of crystallinity of polymer. The highest macrocyclic content (64%) after 7 days of polymerization at 80 °C was observed for [bmim][NTf₂]. For [bmim][PF₆], the macrocyclic content value was not dependent on the reaction time and remained at a similar level (10–14% at 80 °C). The results of degradation test revealed that hydrolytic degradation of ester bonds is more pronounced for PCLs synthesized in [bmim][NTf₂], due to their lower degree of crystallinity compared with PCLs obtained in [bmim][PF₆]. A high purity, low polydispersity index of the obtained polymers and high yield of the process (ca., 90%) indicate that ionic liquids seem to be promising solvents for the synthesis of biomedical polymers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43728.     

Polymeric ionic liquid modified silica for CO2 adsorption and diffusivity

Two types of polymeric ionic liquids (PILs) modified porous silica for CO₂ sorption were synthesized by the polymerization of dialkylphosphate di‐butyl phosphate [VYIM][Bu₂PO₄] and 1‐allyl‐3‐methylimidazolium tetrafluoroborate [AMIM][BF₄] with alkoxyl‐modified silica. The PILs‐modified silica (SiO₂‐P[VYIM][Bu₂PO₄] and SiO₂‐P[AMIM][BF₄]) were evaluated by CO₂ adsorption isotherms at 273 K for investigating the porous structures. The adsorption and desorption behaviors of CO₂ (at 298, 313, and 333 K) and N₂ (at 313 K) up to 0.2 MPa were also investigated using a gravimetric method. In comparison with bare silica, the grafting of PILs on the support surface leads to a loss of microporosity, resulting in a slight decrease in CO₂ sorption capacity. The difference of CO₂ sorption capacity between SiO₂‐P[VYIM][Bu₂PO₄] and SiO₂‐P[AMIM][BF₄] is little, especially under 0.1 MPa. CO₂/N₂ selectivity is however notably improved, and especially [AMIM][BF₄] modified silica shows the best performance. The homogeneous surface diffusion model (HSDM) was used to estimate the diffusivities and good agreement between experimental values and fitting curves was obtained. The diffusion coefficients of CO₂ in the PILs‐modified silica are level with that of bare silica at level of 10⁻⁷−10⁻⁸ m²/s, about two to three orders of magnitude faster than that of reported [BMIM][BF₄]. POLYM. COMPOS., 38:759–766, 2017. © 2015 Society of Plastics Engineers     

Negative effect of [bmim][PF6] on the catalytic activity of alcohol dehydrogenase: mechanism and prevention

BACKGROUND: [bmim][PF₆] is a hydrophobic ionic liquid which could be considered as an environmentally friendly solvent for biocatalysis. In pure [bmim][PF₆], however, alcohol dehydrogenase from yeast (YADH) has no catalytic activity. The aim of the present work was (1) to quantitatively study the negative effect of [bmim][PF₆] on the catalytic activity of YADH and the related mechanism and (2) to made an attempt to lessen the negative effect of [bmim][PF₆] on YADH by microemulsifying [bmim][PF₆]. RESULTS: The activity of YADH in the homogeneous solution formed by H₂O, CH₃CH₂OH and [bmim][PF₆] decreased rapidly with the increase of the molar fraction of [bmim][PF₆]. The inhibitory effect of [bmim][PF₆] on YADH was probably caused by the competition of the imidazole group of [bmim][PF₆] with the coenzyme NAD⁺ for the binding sites on YADH. In a water‐in‐[bmim][PF₆] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonX‐100, which separated YADH from [bmim][PF₆] and avoided the direct inactivation of [bmim][PF₆] on YADH. Under optimal conditions, the activity of YADH was as high as 51 µmol L^?1 min^?1. CONCLUSION: [bmim][PF₆] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright © 2008 Society of Chemical Industry     

Transition‐metal trifluoromethane‐sulphonates‐recyclable catalysts for the synthesis of branched fatty derivatives by Diels‐Alder reactions at unsaturated fatty esters

Diels‐Alder reactions of conjugated linoleic acid ethyl ester (1) with different quinones and with a variety of α/βunsaturated aldehydes and ketones are described in this paper. Using Sc(OTf)₃ or Cu(OTf)₂ as catalysts the reactions can be carried out at 25—40 °C with good yields. For the first time in oleochemistry it is possible to prepare Diels‐Alder cycloadditions with catalyst concentrations of 10 mol‐% instead of stoichiometric amounts of Lewis acids. Furthermore, the reaction time was partly shortened drastically. The catalyst Sc(OTf)₃ can be removed by a simple extraction of the organic layer with water. After evaporation of the aqueous phase to dryness the catalyst can be reused without loss of yield.     

Recycling Chiral Imidazolidin‐4‐one Catalyst for Asymmetric Diels–Alder Reactions: Screening of Various Ionic Liquids

Various imidazolium ionic liquids such as [Bmim]PF₆, [Bmim]SbF₆, [Bmim]OTf and [Bmim]BF₄ were screened for recycling an organic catalyst [(5S)‐5‐benzyl‐2,2,3‐trimethylimidazolidin‐4‐one ( 1 )] for asymmetric Diels–Alder reactions. Good yields and enantioselectivies (up to 85% yield and 93% ee) were obtained from reactions in [Bmim]PF₆ or [Bmim]SbF₆. However, reactions in [Bmim]OTf or [Bmim]BF₄ gave racemic products in low yields. Isolation of the products by simple extraction using diethyl ether allowed recycling of the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.     

Extraction of polycyclic aromatic hydrocarbons from fluid catalytic cracking diesel with ionic liquids

Ionic liquids (ILs) as promising green solvents were first proposed to extract polycyclic aromatic hydrocarbons (PAHs) from fluid catalytic cracking (FCC) diesel. The COSMO-RS model was used for preliminary screening of IL extractants. The liquid–liquid equilibrium (LLE) experiments were performed to show that the IL [BMIM][BF₄] has a high selectivity for the model oil system. Further, the LLE experimental results show that the solubility of 1-methylnaphthalene in [BMIM][BF₄] is relatively low, while the IL exhibits a high selectivity of n-hexadecane to 1-methylnaphthalene. This means that the use of [BMIM][BF₄] can obtain the high-purity products when considering the almost nonvolatility of IL. Compared to the benchmark process, the multistage countercurrent–reflux extraction process can improve the PAHs purity by about 2% at the expense of 5.06% total annual cost and 6.42% energy consumption, rendering the use of IL to extract PAHs from FCC diesel more feasible in industry.     

Fatty acid methyl ester heterogeneous self‐metathesis in hydrophobic green solvent: Mass transfer limitations,catalyst recyclability,and stability

The role of room‐temperature ionic liquids (RTILs), [bmim][PF₆] and [bmim][Tf₂N], as reaction media regarding the catalytic activity and stability of methyltrioxorhenium (MTO) supported on ZnCl₂‐modified mesoporous Al₂O₃ has been studied for self‐metathesis of a functionalized olefin, methyl oleate. The humidity influence on the catalytic activity was probed. The catalyst recycling ability and the kinetics of the metathesis reaction using these RTILs were also investigated. It was found that the MTO‐based catalyst was efficient in viscous hydrophobic RTIL solvents. However, their high viscosity was found to increase the mass transfer limitations thus somewhat impacting the reaction kinetics. Nevertheless, better catalyst stability was reached allowing its possible recycling when used in RTIL media.     

Facile and effective promotion of β crystalline phase in poly(vinylidene fluoride) via the incorporation of imidazolium ionic liquids

In this study, a facile and efficient protocol to enhance the β‐phase content of poly(vinylidene fluoride) (PVDF) is developed, in which the effect of room temperature ionic liquids (RTILs), including [1‐butyl‐3‐methylimidazolium (bmim)][PF₆], [bmim][BF₄], [bmim][FeCl₄] and [bmim][Cl], on the crystallization behavior of PVDF is investigated. The resulting PVDF/RTIL hybrids are characterized by Fourier transform infrared (FTIR) spectroscopy, XRD, polarized optical microscopy (POM) and DSC. The FTIR spectroscopy and XRD results show that the fraction of β‐phase, F(β), is significantly enhanced by the incorporation of RTILs, specifically from 49.2% for neat PVDF to 92.6% for hybrid filled with 15 wt% [bmim][PF₆]. The analysis of the crystallization behavior based on the DSC tests reveals that the degree of crystallinity increases with incorporation of RTILs, implying that RTILs could act as directing agents to facilitate the crystallization process, which is further evidenced by the POM results. In addition, the non‐isothermal crystallization kinetics of PVDF and PVDF/RTIL composites are investigated by means of DSC and the results indicate that the addition of the RTILs significantly influences the mechanism of nucleation and growth of PVDF crystallites. © 2013 Society of Chemical Industry