The unique nature of H<sup>+</sup>in water

Stoyanov, Evgenii S.; Stoyanova, I. V.; Reed, Christopher A.

doi:10.1039/c0sc00415d

Cited by 82 publications

(109 citation statements)

References 73 publications

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“…This study demonstrates that the potentiometrically determined pK a value in aP IL is linearly related to that in water over aw ide pH range.A ccordingly,w ea lign the pH window of EAN with the water-based pH scale.T he pH window may help refine the conditions for using aP IL for acid-catalyzed reactions and estimate the active species under ag iven set of conditions.T he respective edge values of the window are shown to be governed by the acidity of HNO 3 and the basicity of the C 2 H 5 NH 2 unit of EAN.Therefore,the acidbase properties of PILs can be tuned by choosing appropriate constituent ions.A lthough the stronger acidity of EAN compared to that of water could be attributable to the stronger H + activity in EAN than that in H 3 O + ,t he true solvation state and the structure of H + in EAN should be assessed at the molecular level, ad iscussion which is still ongoing even in water. [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.…”

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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Section: Methodsmentioning

confidence: 99%

A pH Scale for the Protic Ionic Liquid Ethylammonium Nitrate

et al. 2016

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“…Communications between associated ions are not as strong as in molecules, but diverse (Endovitsky et al, 2014a;2014b;Hunenberger and Reif, 2011;Stoyanov et al, 2011;Raiteri et al, 2012;Dave and Dikshit, 2011;Zhang et al, 2012;Mandzhieva et al, 2014;Tertre et al, 2011).…”

Section: Ajabsmentioning

confidence: 99%

?Hemical Equilibrium of Soil Solution in Steppe Zone Soil

Batukaev

Endovitsky²,

Minkina

et al. 2014

American Journal of Agricultural and Biological Sciences

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ABSTRACT, NaCO 3 -, NaSO 4 -, CaOH + , MgOH + . Calculation method is proposed for quantitative assessment of real ion forms in the soil solution of chestnut solonetz soil complex. Were proposed equations to calculate free and associated forms of ions. To solve the equations were used an iteration, a linear interpolation of equilibrium constants, a Method of Ionic Pairs including a law of initial concentration preservation, a law of the operating masses of equilibrium system, the concentration constants of ion pair dissociation on the law of operating masses. Was determined the quantity of ion free form and a coefficient of ion association as ratio of ions free form to analytical content γ e = C ass /C an . The association of ions varies in individual soils and soil layer. Increasing soil solution salinity amplifies the ions association. In form of ionic pairs in soil solution are: 11.8-53.8% of Ca 2+ ; 9.4-57.3% of Mg 2+ ; 0.7-11.9% of Na + ; 2.2-22.3% of HCO 3 -, 11.8-62.7% of SO 4 2-. The ion CO 3 2-is high associated, the share of ions in associated form is up to 92.7%. The degree of soil solution saturation was obtained for three level of approximation accounting on analytical concentration, calculated association coefficient, calculated coefficient of association. Relating to thermodynamic solubility product S 0 , the mathematical product of analytical ionic pairs indicated super saturation of soil solutions up to K 1 = 100, taking into account calculated coefficient of association ion activity super saturation of soil solutions is absent, K 3 ≈1. Only for solonetz chestnut meadow K 3 ≈2-5. The soil solution saturation degree in soil profile and laterally in landscape varies. The quantitative assessment of real ion forms in the soil solution allows explain evolution of landscape of salted soils, structure of soil cover. Calculations fulfilled show that a possibility of soil degradation scenario taking into account the laws of association of ions in soil solution is much more probable and dangerous than it was assessed before. New understanding of water-salt transfer, geochemical barriers and ecological functions of soil will help to improve rainfed and irrigational agriculture.

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“…In soil solutions, electrically neutral ion pairs CaCO 0 3 , CaSO 0 4 , MgCO 0 3 , and MgSO 0 4 are formed, as well as charged ion pairs CaHCO , CaOH + , and MgOH + . Communication between the associated ions in soil solution is much more diverse compared to water systems (Hunenberger and Relf, 2011;Stoyanov et al, 2011;Zhang et al, 2012;Tertre et al, 2011).…”

Section: A-m a Batukaev Et Al: Ion Association In Water Solution mentioning

confidence: 99%

Ion association in water solution of soil and vadose zone of chestnut saline solonetz as a driver of terrestrial carbon sink

Batukaev

Endovitsky²,

Andreev³

et al. 2016

Solid Earth

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Abstract. The assessment of soil and vadose zone as the drains for carbon sink and proper modeling of the effects and extremes of biogeochemical cycles in the terrestrial biosphere are the key components to understanding the carbon cycle, global climate system, and aquatic and terrestrial system uncertainties. Calcium carbonate equilibrium causes saturation of solution with CaCO 3 , and it determines its material composition, migration and accumulation of salts. In a solution electrically neutral ion pairs are formed: CaCO 0 3 , CaSO 0 4 , MgCO 0 3 , and MgSO 0 4 , as well as charged ion pairs CaHCO, CaOH + , and MgOH + . The calcium carbonate equilibrium algorithm, mathematical model and original software to calculate the real equilibrium forms of ions and to determine the nature of calcium carbonate balance in a solution were developed. This approach conducts the quantitative assessment of real ion forms of solution in solonetz soil and vadose zone of dry steppe taking into account the ion association at high ionic strength of saline soil solution. The concentrations of free and associated ion form were calculated according to analytical ion concentration in real solution. In the iteration procedure, the equations were used to find the following: ion material balance, a linear interpolation of equilibrium constants, a method of ionic pairs, the laws of initial concentration preservation, operating masses of equilibrium system, and the concentration constants of ion pair dissociation. The coefficient of ion association γ e was determined as the ratio of ions free form to analytical content of ion γ e = C ass /C an . Depending on soil and vadose zone layer, concentration and composition of solution in the ionic pair's form are 11-52 % Ca 2+ ; 22.2-54.6 % Mg 2+ ;1.1-10.5 % Na + ; 3.7-23.8 HCO 3 . The carbonate system of soil and vadose zone water solution helps to explain the evolution of salted soils, vadose and saturation zones, and landscape. It also helps to improve the soil maintenance, plant nutrition and irrigation.The association of ions in soil solutions is one of the drivers promoting transformation of solution, excessive fluxes of carbon in the soil, and loss of carbon from soil through vadose zone.

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The unique nature of H⁺in water

Cited by 82 publications

References 73 publications

A pH Scale for the Protic Ionic Liquid Ethylammonium Nitrate

A pH Scale for the Protic Ionic Liquid Ethylammonium Nitrate

?Hemical Equilibrium of Soil Solution in Steppe Zone Soil

Ion association in water solution of soil and vadose zone of chestnut saline solonetz as a driver of terrestrial carbon sink

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The unique nature of H+in water

Cited by 82 publications

References 73 publications

A pH Scale for the Protic Ionic Liquid Ethylammonium Nitrate

A pH Scale for the Protic Ionic Liquid Ethylammonium Nitrate

?Hemical Equilibrium of Soil Solution in Steppe Zone Soil

Ion association in water solution of soil and vadose zone of chestnut saline solonetz as a driver of terrestrial carbon sink

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The unique nature of H⁺in water