Protic Ionic Liquids and Ionicity

Abstract

Protic ionic liquids (PILs) are a subset of ionic liquids formed by the equimolar mixing of a Brønsted acid and a Brønsted base. PILs have been categorized as poor ionic liquids. However, the issue of assessing the ionicity of PILs is still a matter of debate. In this work we studied some physicochemical properties of three chosen PILs, namely, ethanolammonium acetate (EOAA), 2-methylbutylammonium formate (2MBAF), and pentylammonium formate (PeAF), at the initial equimolar (stoichiometric) acid/base ratio and in the presence of excess acid and base. DSC phase-transition studies along with NMR, IR, and Raman spectroscopy were performed on the chosen PILs. The results are discussed in terms of the degree of ionization (extent of proton transfer from the Brønsted acid to Brønsted base), and the possibility of the formation of polar 1:1 complexes and larger aggregates in the neat stoichiometric PILs.

High-throughput approach for the identification of anilinium-based ionic liquids that are suitable for electropolymerisation

“…The multiplet peak at B120 ppm is associated with carbon atoms surrounded by three fluorine atoms (-CF 3 ), and the peak at B160 ppm corresponds to a (-COO-) group which are consistent with the formation of a PIL. The conductivity of the n-ethylanilinium TFA PIL was measured to be 5.2 mS cm À1 at room temperature, compared to 1.0 mS cm À1 for N-methylpyrrolidinium TFA and 14.4 mS cm À1 for 2-pyrrolidonium TFA, 17,21,22 which is consistent with the formation of an ionic compound. The combined 1 H NMR and 13 C NMR data indicate that the reaction of n-ethylaniline with TFA took place via proton transfer only, thus forming an ionic compound.…”

Properties of ionic liquids containing silver(I) or protic alkylethylenediamine cations with a bis(trifluoromethanesulfonyl)amide anion

“…On the other hand, protic ionic liquids (PILs) have recently attracted attention for their variable proton activities [34][35][36][37][38][39][40][41][42]. PILs generally have larger polarities [43,44] and tend to dissolve metal salts to a larger extent than common aprotic ionic liquids (AILs).…”

Physicochemical Properties of Ionic Liquids Containing N-alkylamine-Silver(I) Complex Cations or Protic N-alkylaminium Cations

“…That is, the transfer of the proton from the acid to the base was almost complete. (Nuthakki et al, 2007; The solubilities of HexH(TFSA) and EtHexH(TFSA) liquids in various solvents were tested and classified into three categories as follows. They were more than 10% (w/v) in methanol, ethanol, acetone, dichlromethane, ethyl acetate, chloroform, diethyl ether, and 1,4-dioxane, from 0.1% (w/v) to 10% (w/v) in water and benzene, and were less than 0.1% (w/v) in cyclohexane and hexane.…”