H-functionalized Ionic Liquids Research Articles

Regulating the Acidity of SO3 H-Functionalized Ionic Liquids: Hydrogen Bonding or Electrostatic Potential?

The SO3 H-functionalized ionic liquids (ILs) with high acidity are important catalysts for acid-catalyzed reactions. However, the acidity of these ILs have been found to decrease due to intramolecular hydrogen bonds (H-bonds). In this work, a series of anionic SO3 H-functionalized ILs were designed and the factors resulting in weak acidity were investigated, including H-bonds strength and electrostatic potential on the leaving proton (ESPLP). Using catalytic experiment, atoms in molecules topology analysis and electrostatic potential calculation, it was found that the acidity of ILs was correlated with the value of ESPLP rather than the H-bond strength. Meanwhile, there were several ways to increase the acidity of anionic SO3 H-functionalized ILs, such as enhancing the electron-withdrawing ability of cation, introducing H-bond acceptor sites on cation or separating the intramolecular H-bonds through substitution position. These strategies made the conversion of TBA in Friedel-Crafts alkylation increase from 19 % to 84 %.

Multiple-SO3H functionalized ionic liquid as efficient catalyst for direct conversion of carbohydrate biomass into levulinic acid

• Synthesis and characterization of SO 3 H-functionalized ionic liquids. • Efficient conversion of cellulose to levulinic acid using SO 3 H-functionalized ionic liquids. • The yield of LA is up to 65% at the optimum condition with using [BSim]HSO 4 as catalyst. • The [BSim]HSO 4 was easily recycled and showed high catalytic activity even after four cycles. A series of new SO 3 H-functionalized ionic liquids (ILs) were synthesized and characterized, which were successfully applied to catalyze cellulose to produce levulinic acid (LA) via one-pot reaction. The structure, thermal property, and acidity of ILs were characterized by NMR, TGA, and Hammett acidity measurement. The Hammett acidity (H 0 ) of ILs increase in the following order: [BSim]H 2 PO 4 <[BSim]TsO < [BSim]CF 3 SO 3 < [BSim]HSO 4 , which is consistent with their yield of LA order using these ILs as catalysts. Under the optimum conditions, the yield reached up to 65% when [BSim]HSO 4 was used as catalyst and solvent, which is one of the best results compared to those reported in literature. Moreover, the ILs were easily recycled without structural change even after four cycles, and the yield of LA was up to 44% at the fifth cycle. Furthermore, TGA indicated that these SO 3 H-functionalized ILs exhibited excellent thermal stability. These efficient ILs will provide new options for converting biomass resources to LA and other chemicals.

Synthesis of alkyl polyglycosides using SO3H-functionalized ionic liquids as catalysts.

An effective process for synthesis of alkyl polyglycosides (APG) was developed using SO3H-functionalized ionic liquids (SFILs) as catalysts. Four SFILs, [PSmim][HSO4], [PSmim][pTSA], [PSPy][HSO4] and [PSPy][pTSA], were designed and synthesized for APG synthesis. The results indicated that [PSmim][HSO4] shows the best catalytic performance among these four SFILs, which has a great agreement with the order of their acidities. When the [PSmim][HSO4] was used as catalyst, the reaction time could be decreased from 24 h to 8 h, and molar ration of n-octanol to glucose could be decreased from 5 : 1 to 3 : 1 under the optimization reaction conditions. In addition, the [PSmim][HSO4] could be easily regenerated and recycled at least 5 times with slight decrease in catalytic activity. Moreover, the catalytic mechanism of [PSmim][HSO4] was further investigated by molecular simulation. The high catalytic activity of [PSmim][HSO4] is attributed to hydrogen bonds between [PSmim][HSO4] and glucose and n-octanol, which could accelerate the protonation of glucose and removal of hydrogen ions from the hydroxyl in n-octanol.

Understanding Structure–Property Relationship of SO3H-Functionalized Ionic Liquids together with Sulfuric Acid in Catalyzing Isobutane Alkylation with C4 Olefin

In this work, the SO3H-functionalized ionic liquids (SFILs) ([CnPSIm][HSO4], n = 1, 2, 4, 6, and 8) were investigated as cocatalyst mixed with the concentrated H2SO4 for the isobutane alkylation. The SFILs with longer alkyl chain show a better catalytic performance with the C8 selectivity up to 75.73 and RON up to 95.66, respectively. The better catalytic performance can be attributed to the better dispersion of isobutane in the SFIL/H2SO4 system led by the SFILs with longer alkyl chain, which is further correlated with the nanostructured-aggregation feature of the longer alkyl chain confirmed by MD simulation. In addition, the reusability of SFIL/H2SO4 mixture can reach up to 22 runs, outclassing the pure H2SO4. The MD simulation, quantum chemistry calculations, and 1H NMR spectra revealed that cationic clusters are formed by the strong hydrogen bonds between the sulfonic acid group and the H2SO4, which is beneficial to the longer lifetime of the SFIL/H2SO4 mixtures. Hopefully, the useful information in ...

Synthesis of 4,4′-Methylenedianiline Catalyzed by SO3H-Functionalized Ionic Liquids

4,4′-Methylenedianiline (4,4′-MDA) is a key intermediate for the production of polyurethanes. A series of SO3H-functionalized ionic liquids (SFILs) were synthesized, and their catalytic performance was evaluated in the condensation reaction of aniline with formaldehyde for the synthesis of 4,4′-MDA. The result showed that SFILs had excellent catalytic activity, and their catalytic activity was consistent with their acid strength. [HSO3-bmim]CF3SO3 (SImTf) with the highest acid strength showed the best catalytic activity. Then, the influence of reaction conditions on the condensation reaction of aniline with formaldehyde to 4,4′-MDA was investigated using SImTf as the catalyst, and suitable reaction conditions were obtained as follows: molar ratio of aniline to formaldehyde = 5, mass ratio of SImTf to formaldehyde = 3.5, reaction temperature of 80 °C, and reaction time of 8 h. Under the above reaction conditions, the conversion of aniline was 36.3%, and the yield and selectivity of 4,4′-MDA were 79.4% and ...

Synthesis and Physicochemical Properties of Two SO3H-Functionalized Ionic Liquids with Hydrogen Sulfate Anion

Two SO3H-functionalized ionic liquids (ILs), N-isobutyl-3-sulfopropan-1-aminium hydrogen sulfate [IBAC3S]HSO4 and N-isobutyl-4-sulfobutan-1-aminium hydrogen sulfate [IBAC4S]HSO4, were synthesized and characterized by NMR and HR-MS. The thermal properties and acidities were analyzed. Density, dynamic viscosity, surface tension, conductivity, and refractive index of the IL were studied as a function of temperature. The physicochemical properties, namely molecular volume, isobaric coefficients of thermal expansion, standard entropy, critical temperature, molar free volume, interstice volume, etc. of the IL were estimated according to the reported empirical and thermodynamic equations. On the basis of the Walden rule, the ionicty of the two SO3H-functionalized ionic liquids was assessed by the product of molar conductivity and viscosity.

Efficient and selective alcoholysis of furfuryl alcohol to alkyl levulinates catalyzed by double SO3H-functionalized ionic liquids

The production of alkyl levulinates from furfuryl alcohol (FAL) in alcohol media was investigated at moderate temperature in the presence of Bronsted acidic ionic liquids. The reaction was examined and optimized under batch conditions, where it was found that furfuryl alcohol was rapidly and almost quantitatively converted into intermediate products including 2-alkoxymethylfuran and 4,5,5-trialkoxypentan-2-one, and high alkyl levulinates yield of 95% can be achieved after reaching a steady state in 2 h. An advantage of this catalyst system is that undesired dialkyl ether (DEE) formed by a side reaction of the dehydration of alcohol is negligible. The Hammett method was used to determine the acidities of these ionic liquids, which indicated that the acidity and the molecular structure have strong effects on the catalytic activity of ionic liquids. Based on the experimental results, a possible mechanism for the alcoholysis of FAL is proposed.

Synthesis of SO3H-Functionalized Ionic Liquids and Their Novel Application in Removal of Trace Olefins from Aromatics

The novel ionic liquids with an alkane sulfonic acid group were prepared and used for removal of trace olefins from aromatics (referred to as oil). The structures and acidities of the ionic liquids were experimentally characterized and systematically analyzed. The influences of various reaction parameters, such as the stirring speed, viscosities of the ionic liquids, molar fraction of ZnCl2, dosage and type of ionic liquid, reaction temperature, reaction time, and the reusability of the ionic liquid, were investigated. It was found that the ionic liquid 1-(3-sulfopropyl)-3-methylimidazolium bromochlorozincinate ([C3SO3Hmim]Br-ZnCl2) with the molar fraction of ZnCl2 of 0.67 exhibited a better performance for olefin removal. Meanwhile, the experimental results showed that after the reaction had taken place at 373 K for 1 h, olefin conversion of 29.54% was obtained with the mass ratio of IL to oil of 0.2. Even though the reusability of the ionic liquid was not good, the separation of the reaction mixture can be performed by simple decantation.

ChemInform Abstract: Novel SO3H‐Functionalized Ionic Liquids Catalyzed a Simple, Green and Efficient Procedure for Fischer Indole Synthesis in Water under Microwave Irradiation.

Abstract Novel SO 3 H-functionalized ionic liquids were successfully applied as catalysts for one-pot Fischer indole synthesis under microwave irradiation and in a water medium. Various types of indoles were prepared using single-carbonyl ketones/aldehydes or cyclohexandiones with aryhydrazine hydrochlorides in 86–96% yields in water under microwave irradiation. The indole products could be conveniently separated from the reaction mixture through filtration, and the catalytic system of [(HSO 3 -p) 2 im][CF 3 SO 3 ]/H 2 O could be reused directly without any treatment. The entire process is simple, time saving, and environmentally friendly.

The Novel SO3H-Functionalized Ionic Liquids Promoted Synthesis of Xanthenedione Derivatives in Aqueous Media under Microwave Irradiation

Novel SO3H-functionalized ionic liquids were successfully applied as catalysts for synthesis of xanthenediones under microwave irradiation in Aqueous. Various types of Xanthenes were provided in 90-97% yields using the catalytic system of [(HSO3-p)2im][CF3SO3]/H2O. The products could be conveniently separated from the reaction mixture by filtration and the dissolved catalyst could be reused without any treatment, which of the separation process was performed in water without using any organic solvents. The method not only has the adventages of shrot time and simple operation, but also is environmentally friendly.

Microwave-accelerated esterification of salicylic acid using Brönsted acidic ionic liquids as catalysts

abstract A variety of Bronsted acidic ionic liquids were screened as catalysts for the esterification of salicylic acid.The experimental results indicated that SO 3 H-functionalized ionic liquids with HSO 4 performed high cat-alytic activity under microwave irradiation, and the yields can reach 91.9–93.6%. Furthermore, ionic liq-uids can be easily separated by simple decantation and have a fair reusability. The Bronsted acidity–catalytic activity relationships were also investigated and the results showed that the activity of theacidic ionic liquids is in excellent agreement with their acidity order.Crown Copyright 2010 Published by Elsevier B.V. All rights reserved. 1. IntroductionAs fine chemicals, methyl salicylate (MS) has been widely usedas flavor and fragrance agent, cosmetic and dye carrier, as well asultraviolet (UV)-light stabilizer in acrylic resins [1]. Fisher esterifi-cation is one of the simplest methods to obtain this ester. However,these reactions usually employ mineral acids, such as H

Synthesis of chalcones via Claisen–Schmidt condensation reaction catalyzed by acyclic acidic ionic liquids

Abstract Some recyclable acyclic SO 3 H-functionalized ionic liquids have been used as catalysts for the synthesis of chalcones by Claisen–Schmidt condensation. The chalcones could simply be separated from the catalyst by decantation. After removal of the water from the reaction mixture the catalysts could be recycled and reused for several times without noticeably decreasing the catalytic activity.

SO3H-functionalized ionic liquids for selective alkylation of m-cresol with tert-butanol

The SO 3 H-functionalized ionic liquids were synthesized by using tri-alkylamine and 1,4-butanesultone as the source, and characterized by NMR and TOF-MS, and their catalytic performance for the tert -butylation of m-cresol with tert -butanol (TBA) were investigated. The reaction time, reaction temperature, molar ratio of m-cresol to TBA, and the recycle number of the spent ionic liquid were examined. Under optimum reaction conditions, the conversion of m-cresol and the selectivity to 2- tert -butyl-5-methyl phenol (2-TBC) were 81% and 96%, respectively. No apparent loss of activity and selectivity of the ionic liquid were observed after four recycles. The acidity of ionic liquids determined by Hammett method is about the same as that of conventional acid, such as H 2 SO 4 . The possible mechanism for this reaction system was discussed based on the reaction results and the ab initio calculation results.

Selective alkylation of phenol with tert-butyl alcohol catalyzed by Brönsted acidic imidazolium salts

Abstract Alkylation reaction of phenol with tert -butyl alcohol (TBA) catalyzed by SO 3 H-functionalized ionic liquids has been investigated. The influences of different ionic liquids, reaction time, reaction temperature, reactant ratio (mole ratio of phenol to that of TBA), the amount and the recycle of ionic liquid were studied. The conversion of phenol and the selectivity of 2,4-DTBP were 80.4 and 60.2%, respectively, under optimum reaction condition. At the same time, the reaction mechanism was discussed based on the distribution of products.

Esterification of aliphatic acids with olefin promoted by Brønsted acidic ionic liquids

Addition reactions of aliphatic acids with olefins to give corresponding esters have been investigated using SO3H-functionalized ionic liquids as dual catalyst–solvent. The isolation of the desired products could be achieved via simple decantation and ionic liquids could be reused continuously after dried in vacuum (5–12 mmHg) at ca. 80 °C.