Acidity and Basicity of Aqueous Mixtures of a Protic Ionic Liquid, Ethylammonium Nitrate

Kanzaki, Ryo; Uchida, Kuniaki; Song, Xuedan; Umebayashi, Yasuhiro; Ishiguro, Shin‐ichi

doi:10.2116/analsci.24.1347

Cited by 54 publications

(58 citation statements)

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“…[11][12][13] On the other hand, MacFarlane et al have shown that the proton transfer of HB + to A -proceeds in the pyrrolidinium based ionic liquids (smaller pKs), though the ΔpKa value is 5.7, which means significant amount of neutral species [B] and [HA] ] ionic liquid by a direct potentiometry with the IS-FET (ion selective field effective transistor) and Pt(H2) electrodes. 15,16 Actually, the pKs values of 10.004 with the IS-FET electrode and 9.83 with Pt(H2) one, respectively, are significantly different from the ΔpKa value of 11.93. It is thus important to determine pKs values of ionic liquids directly.…”

Section: Introductionmentioning

confidence: 93%

Physicochemical and Acid-base Properties of a Series of 2-Hydroxyethylammonium-based Protic Ionic Liquids

et al. 2012

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Section: Introductionmentioning

confidence: 93%

Physicochemical and Acid-base Properties of a Series of 2-Hydroxyethylammonium-based Protic Ionic Liquids

et al. 2012

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“…[14] Experimental Section EAN was prepared from aqueous ethylamine and nitric acid. [15] The water content determined by aKarl Fisher method was 80-200 ppm. This amount of water hardly affects acid-base equilibria in an EANwater mixture,even if it seems non-negligible in aconcentration unit (a few tens mmol dm À3 ).…”

Section: Methodsmentioning

confidence: 99%

“…This amount of water hardly affects acid-base equilibria in an EANwater mixture,even if it seems non-negligible in aconcentration unit (a few tens mmol dm À3 ). [7,15] Other chemicals of analytical grade (> 99 %) were used without further purification. Potentiometric titrations were carried out with the electromotive force (emf) measurements by using the electrochemical cell representedas: Ag=AgCl j 0:1 m NaCl ðaqÞkEAN k sample EAN solution j Pt ðH 2 Þ where the double bars correspondtoaliquid junction with a4G glass filter.T he cell gave as atisfactorily stable emf within 5-10 min.…”

Section: Methodsmentioning

confidence: 99%

A pH Scale for the Protic Ionic Liquid Ethylammonium Nitrate

et al. 2016

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To quantify the properties of protic ionic liquids (PILs) as acid-base reaction media, potentiometric titrations were carried out in aneat PIL, ethylammonium nitrate (EAN). Al inear relationship was found between the 14 pK a values of 12 compounds in EAN and in water.I no ther words,t he pK a value in EAN was found to be roughly one unit greater than that in water regardless of the charge and hydrophobicity of the compounds.Itispossible that this could be explained by the stronger acidity of HNO 3 in EAN than that of H 3 O + in water and not by the difference in the solvation state of the ions. The pH value in EAN ranges from À1t o9o nt he pH scale based on the pH value in water.Protic ionic liquids (PILs) function as H + carriers and/or reservoirs for dissociable hydrogen ions (H + )a nd have several industrial applications,f or example in fuel cell electrolytes.I ns ome PILs,p rotons are considered to be transferred through ap roton-hopping mechanism.[1] For organic syntheses,P ILs exhibit the desirable properties of ionic liquids,s uch as an egligible volatility and thermal and chemical stability.Inaddition, PILs themselves can act as the catalyst in acid-catalyzed reactions,w here the Brønsted/ Lewis acidity of the PILs determines the reaction pathway and the catalytic activity.[2] However,f ew reported studies have addressed the acid-base properties of PILs.Acid-base reactions are of general interest across the field of chemistry because the reactant is reversibly charged or can be neutralized by H + association or dissociation, drastically changing its reactivity or behavior. Thus the acid-base properties of PILs have attracted attention as akey characteristic of the compounds.[3] Although there are certain studies evaluating experimentally the acid-base equilibria in ionic liquids, [4] it remains difficult to compare directly the pH value in aP IL with that in water. This is mainly due to the wide pH range,f rom acidic to basic, caused by autoprotolysis, aunique equilibrium in amphoteric solvents such as PILs.T o determine the pH value particularly in H + -deficient solutions, the autoprotolysis constant have been already determined in some PILs. [5][6][7][8] Thepurpose of this study is to establish apHscale that is universally applicable to protic solvents,b oth molecular and ionic. To do this,wedetermined 14 acid dissociation constants of 12 compounds in the neat PIL ethylammonium nitrate (EAN) by means of potentiometric titrations with ahydrogen electrode.EAN was described first in 1914 [9] and is considered atypical PIL whose physicochemical properties are the most widely understood. Many thorough investigations,f rom the macroscopic [10] to the molecular level, [11] indicated that EAN provides water-like solvation conditions.A sa na cid-base medium, its autoprotolysis constant was experimentally determined by us [6,7] and by Letellier et al. [5] In the present study,weinvestigate the pH scale in EAN with respect to the unified pH scale based on water. This enables us to compare the pH values...

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“…Kanzaki et al [89] reported EAN composed of C 2 H 5 NH 3 + and NO 3 − ions, which behave as an acid and a base, respectively, and reported that H 3 O + is a stronger acid than HNO 3 in an EAN solution, unlike in water.…”

Section: Applications Of Ammonium-based Ionic Liquidmentioning

confidence: 99%

Ammonium- and Phosphonium-Based Ionic Liquid: Green and Reusable Catalysts

Sarda¹,

Wasmatkar²,

Jadhav³

et al. 2014

Green Chemistry: Synthesis of Bioactive Heterocycles

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Recently, the use of ionic liquids (ILs) attracted an increasing interest in the field of organic synthesis because of its mild reaction condition, negligible vapor pressure, solvating ability, and easy recyclability. ILs are used as green reaction media due to their unique chemical and physical properties such as non-volatility, noninflammability, thermal stability, and controlled miscibility. Today, they have a wider scope, playing significant role in reactions as a solvent as well as catalyst. Several reactions have been recently reported using ILs as reaction media and rate enhancers. In chemical and pharmaceutical industries, there is always a demand for

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Acidity and Basicity of Aqueous Mixtures of a Protic Ionic Liquid, Ethylammonium Nitrate

Cited by 54 publications

References 20 publications

Physicochemical and Acid-base Properties of a Series of 2-Hydroxyethylammonium-based Protic Ionic Liquids

Physicochemical and Acid-base Properties of a Series of 2-Hydroxyethylammonium-based Protic Ionic Liquids

A pH Scale for the Protic Ionic Liquid Ethylammonium Nitrate

Ammonium- and Phosphonium-Based Ionic Liquid: Green and Reusable Catalysts

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