Do anions influence the polarity of protic ionic liquids?

Abstract

Polarity studies in two classes of imidazolium-based protic ionic liquids (PILs) possessing [HSO(4)](-), [HCOO](-), [CH(3)COO](-) and [CH(3)CH(2)COO](-) anions were carried out using a solvatochromic method from 298.15 to 353.15 K. For 1-methylimidazolium class of PILs, E(T)(30) was found to be independent over the entire range of temperature, while E(T)(30) was noted to decrease with a rise in temperature in the case of 1-butylimidazolium class of PILs containing [CH(3)COO](-) and [CH(3)CH(2)COO](-) anions. The E(T)(30) value decreases in both the classes upon varying the anions ([HSO(4)](-), [HCOO](-), [CH(3)COO](-) and [CH(3)CH(2)COO](-)). The E(T)(30) value is controlled by hydrogen bond acceptor basicity, β, and dipolarity/polarizability, π*. The E(T)(30) value for PILs varies inversely to the strength of the coulombic interaction between ions in PILs. Strong interactions between ions lead to lower E(T)(30) values. Unlike the poor thermal effect on E(T)(30), the Kamlet-Taft parameters i.e. α, β and π* have pronounced thermal effect in the imidazolium-based PILs. Variation in the Kamlet-Taft parameters is controlled by the stabilization of ions and the degree of proton transfer from Brønsted acid to Brønsted base.

Oxygen Reduction Reaction in Ionic Liquids: An Overview

“…18.10). This enhancement in performance, similar to that produced by the is inferior than that of ethylene glycol in the same IL which was corroborated by experimental calculation of the hydrogen-bond donating ability using the Kamlet-Taft parameters [29,30]. Interestingly, the oxygen reduction reaction in [P 66614 ][Cl]/ethylene glycol mixture using a glassy carbon working electrode follows an overall 4-electron pathway (i.e.…”

Solvent-mediated molar conductivity of protic ionic liquids

“…The protic ionic liquids, [ [36][37][38] The PILs were synthesized by neutralization reaction of acid and base. Dropwise addition of base to acid was carried out in an ice bath to avoid heat generation due to the exothermic reaction.…”

Water sorption in protic ionic liquids: correlation between hygroscopicity and polarity

“…15 This behavior was later studied by Cuadrado-Prado et al in eight imidazolium-based ILs in 2009. For example, imidazolium-based PILs were found to be good catalytic media for carbon-carbon bond, carbon-oxygen bond, and carbonnitrogen bond forming reactions; [23][24][25] superbase-based PILs could be well tuned in their basicity for CO 2 capture with a faster absorption rate and greater absorption capacity; 26 and distillable PILs have been successfully applied for recycling raw materials in BASF. 17 Recently, we investigated the water sorption process in 18 conventional ILs with varying structures (anion, cation, alkyl chain length, and C2 methylation at imidazolium ring) and experimental conditions (temperature and relative humidity).…”