Determination of an Acidic Scale in Room Temperature Ionic Liquids

Thomazeau, C.; Olivier‐Bourbigou, Hélène; Magna, Lionel; Luts, Stéphane; Gilbert, Bernard

doi:10.1021/ja0297382

Cited by 410 publications

(264 citation statements)

References 13 publications

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“…Since no additional peaks were seen around the melting points of pure 18C6 (39)(40) • C) and pure HTf 2 N (52-56 • C), neither 13 C NMR, and (c) 19 Fig. 5c displays 19 F NMR which exhibits a singlet at −79.79 ppm, the region characteristic of ionic CF 3 SO 2 derivatives: they fall between −71 ppm and −80 ppm (CFCl 3 ), shifting to a higher field as the charge on the CF 3 SO 2 group increases.…”

Section: Synthesis Of [H 3 Omentioning

confidence: 95%

A Hydronium Solvate Ionic Liquid: Facile Synthesis of Air-Stable Ionic Liquid with Strong Brønsted Acidity

Kitada

Takeoka

Kintsu

et al. 2018

J. Electrochem. Soc.

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A new kind of ionic liquid (IL) with strong Brønsted acidity, i.e., a hydronium (H 3 O + ) solvate ionic liquid, is reported. The IL can be described as [H 3 When two or more kinds of substances are mixed, the properties of the mixture can differ from those of the pure substances. Depending on the interactions between the components, some components undergo ionization, e.g. dissociation, protonation, solvation and complexation, due to the neutralization of Brønsted or Lewis acids and bases. Sometimes, the acid-base mixtures can be categorized as ionic liquids (ILs) with melting points below 100• C, which consist only of cations and anions. ILs are regarded as "the third liquid" and some ILs have fascinating physicochemical properties, such as low volatility, low flammability, high chemical, and thermal stability. Furthermore, ILs have received growing interest due to their various uses as media in chemical, biochemical, and/or electrochemical systems. [1][2][3][4][5][6] Common anions of ILs such as BF 4 -, PF 6 -, and AlCl 4 -are produced by neutralization, i.e. the adducts of a Lewis acid (BF 3 , PF 5 , or AlCl 3 ) and a Lewis base (F -or Cl -). Examples of ILs prepared through neutralization include solvate ILs.7-13 Solvate ILs often consist of equimolar molten mixtures of polyethers (linear or cyclic ones, i.e. glymes or crown ethers) and certain metal salts, where the Lewis acidic metal cations are solvated by equimolar amounts of Lewis basic glymes to give complex cations. Besides, neutralization of Brønsted acids and bases produces so-called protic ILs, which are preferred as acid-catalyzed reaction media due to the presence of an acidic proton.3-6 Since proton transfer is a common chemical transformation, Brønsted acidic ILs receive research attention especially for acid catalysts, fuel cells, biomass processing, polymerization, CO 2 fixation, etc.6,14-19 The design of stronger Brønsted acidic ILs and evaluation of the acidity in ILs are important for exploring their possible applications as media for acid-base reactions.Although 21-24 However, there is an exception. In solid, anhydrous HTf 2 N, the proton is bonded to the anion nitrogen and two oxygens of a neighboring HTf 2 N molecule. 25 Likewise, in the case of monohydrate, the imide superacid HTf 2 N remains associated and does not protonate water, as suggested experimentally and theoretically. In the infrared measurements for an H 2 O and HTf 2 N mixture in CCl 4 , strong Fermi resonance for N-H vibrations serves as evidence that HTf 2 N remains * Electrochemical Society Member.z E-mail: kitada.atsushi.3r@kyoto-u.ac.jp intact, and from the ab initio calculations, spontaneous proton dissociation was not observed for the Fig. 1a

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Section: Synthesis Of [H 3 Omentioning

confidence: 95%

A Hydronium Solvate Ionic Liquid: Facile Synthesis of Air-Stable Ionic Liquid with Strong Brønsted Acidity

Kitada

Takeoka

Kintsu

et al. 2018

J. Electrochem. Soc.

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“…Based on the protocol given by Gilbert et al, [33] the acidities of these Brønst-ed-acidic ILs were characterized using UV/Vis spectroscopy with p-nitroaniline as the indicator and molecular probe. Therein, the ILs and 4-nitroaniline were dissolved in methanol with concentrations of 3.0 10 À2 mol L À1 and 7.5 10 À5 mol L À1 , respectively.…”

Section: Hammett Acidity Of Brønsted-acidic Ilsmentioning

confidence: 99%

Efficient and Selective Dehydration of Fructose to 5‐Hydroxymethylfurfural Catalyzed by Brønsted‐Acidic Ionic Liquids

2010

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The dehydration of D‐fructose and glucose has been studied with acidic ionic liquids as catalysts. A series of Brønsted‐acidic ionic liquids has been synthesized and tested in the dehydration of D‐fructose. The results showed that N‐methyl‐2‐pyrrolidonium methyl sulfonate [NMP]+[CH3SO3]− and N‐methyl‐2‐pyrrolidonium hydrogen sulfate [NMP]+[HSO4]− have high catalytic activity. Highly efficient and selective dehydration of D‐fructose to 5‐hydroxymethylfurfural (HMF) was achieved in dimethyl sulfoxide (DMSO) under mild conditions. For example, a 72.3 % yield of HMF with 87.2 % selectivity were obtained for 2 h at 90 °C in the presence of 7.5 mol % [NMP]+[CH3SO3]−. The effects of the reaction temperature, time, and solvent were investigated in detail. The catalyst and solvent can be recycled for the dehydration of D‐fructose. The Hammett method was used to determine the acidities of these ionic liquids, which indicated that the acidity and molecular structure have strong effects on the catalytic activity of ionic liquids. Based on the experimental results, a possible reaction mechanism for the dehydration of D‐fructose is proposed.

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“…The acidity strength of an acid can be expressed by Hammett function using UV-visible spectrophotometry. For example, the acidity measurement of nonchloroaluminate ILs had been performed successfully utilizing UV-visible spectroscopy with Hammett indicator method [20], and this method was applied to determine the acidity of protic pyridinium ILs, Brønsted acidic ILs, and the strength of carboxylic acids in different ILs [21][22][23][24].…”

Section: Acidity Determination Of the Ilsmentioning

confidence: 99%

Caprolactam-Based Brønsted Acidic Ionic Liquids for Biodiesel Production from Jatropha Oil

et al. 2017

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Abstract:Caprolactam-based ionic liquids show many advantages, such as the lower toxicity, lower cost, and a simple preparation process. In this work, caprolactam-based ionic liquids were prepared and adopted as catalysts for the transesterification of Jatropha oil with methanol. The results demonstrated that the SO 3 H-functional caprolactam-based ionic liquids have higher catalytic activity than those of the caprolactam-based ionic liquids without sulfonic group or the SO 3 H-functional pyridine -based ionic liquids, attributed to their stronger Brønsted acidity. By optimizing the reaction parameter, the biodiesel yield catalyzed by 1-(4-sulfonic group) butylcaprolactamium hydrogen sulfate ([HSO 3 -bCPL][HSO 4 ]) could reach above 95% at 140 • C for 3 h. Furthermore, the ionic liquid had a good reusability.

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Determination of an Acidic Scale in Room Temperature Ionic Liquids

Cited by 410 publications

References 13 publications

A Hydronium Solvate Ionic Liquid: Facile Synthesis of Air-Stable Ionic Liquid with Strong Brønsted Acidity

A Hydronium Solvate Ionic Liquid: Facile Synthesis of Air-Stable Ionic Liquid with Strong Brønsted Acidity

Efficient and Selective Dehydration of Fructose to 5‐Hydroxymethylfurfural Catalyzed by Brønsted‐Acidic Ionic Liquids

Caprolactam-Based Brønsted Acidic Ionic Liquids for Biodiesel Production from Jatropha Oil

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