Hydrogen‐Bonding‐Driven Ion‐Pair Formation in Protic Ionic Liquid Aqueous Solution

Abstract

Protic ionic liquids (PILs) in solution especially in water have attracted more and more attention due to their unique properties. The solvation of PILs in water is important to their properties and applications. To explore the solvation of bio‐based PILs in water, acidity of 49 [AA]X amino acid ionic liquids (AAILs) consisting of 7 different cations and 7 different anions was studied as a favorable probe. The pKa values for [AA]X PILs containing same cations were obtained and discussed. The acidity strength of the [AA]X PILs varies with both cation and anion which does not follow the conventional assumption that the acidity for PILs is independent of anions. The acidic discrepancy of [AA]X PILs aqueous solution is probably mediated by the formation of ion pairs according to a revised solvation model of PILs. Quantum‐chemistry calculation was employed to unpuzzle anion's different effects on the acid balance of cations where cation‐anion hydrogen bonds play an important role. Such difference in acidity allows us to understand the formation of solvated ion pairs. This work provides an insight into the fundamental solvation of PILs from acid perspective and their influence on acidity properties for the first time.

The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids

“…To systematically explore the acidity of The relationship between the acidity and concentration is important for many applications, such as catalysis [9,37,51]. The H 0 of [ValC 1 ]NO 3 and [PheC 1 ]NO 3 in aqueous solutions at various concentrations were measured.…”

“…An accurate p K a value is important to select reaction conditions in catalytic chemistry [ 27 , 31 , 32 , 33 ]. Determining the acidity of ILs in water and ethanol has become an intriguing topic, since water and ethanol are promising media for green chemistry [ 30 , 34 , 35 , 36 , 37 ]. Herein, four different methods were employed to study the Brønsted acidity of [AAE]X PILs with different amino acid ester cations and anions in water and ethanol carried out.…”

Electrochemical conversion of CO2 in non‐conventional electrolytes: Recent achievements and future challenges

“…Similar to organic solvents, very few works have investigated the CO 2 RR in ILs from the fundamental atomistic point of view, using in situ spectroscopic techniques or theoretical calculations. [ 95–97 ] We will mention the work of Papasizza et al. implementing in situ ATR SEIRAS to understand the changes in the structure of the double‐layer during the CO 2 RR to CO in ILs and ionic‐liquid/water mixtures.…”

“…Similar to organic solvents, very few works have investigated the CO 2 RR in ILs from the fundamental atomistic point of view, using in situ spectroscopic techniques or theoretical calculations. [95][96][97] We will mention the work of Papasizza et al implementing in situ ATR SEIRAS to understand the changes in the structure of the double-layer during the CO 2 RR to CO in ILs and ionic-liquid/water mixtures. [98] The in situ ATR SEIRAS experiments revealed two types of water in the [EMIM]BF4/water mixture, with different degrees of hydrogen bonding at the interface: water in water-rich regions (bulk-like water) and water in a [EMIM]BF4-rich environment.…”

Effect of hydrophobic ionic liquids aqueous solubility on metal extraction from hydrochloric acid media: Mathematical modelling and trivalent thallium behavior

“…The corresponding dissociation constant, K a Hbet + , is also known [36,37] and the average value at room temperature based on literature data is (1.12 ± 0.10)10 -2 mol dm -3 .…”