A Simple Halide-to-Anion Exchange Method for Heteroaromatic Salts and Ionic Liquids

Abstract

A broad and simple method permitted halide ions in quaternary heteroaromatic and ammonium salts to be exchanged for a variety of anions using an anion exchange resin (A− form) in non-aqueous media. The anion loading of the AER (OH− form) was examined using two different anion sources, acids or ammonium salts, and changing the polarity of the solvents. The AER (A− form) method in organic solvents was then applied to several quaternary heteroaromatic salts and ILs, and the anion exchange proceeded in excellent to quantitative yields, concomitantly removing halide impurities. Relying on the hydrophobicity of the targeted ion pair for the counteranion swap, organic solvents with variable polarity were used, such as CH3OH, CH3CN and the dipolar nonhydroxylic solvent mixture CH3CN:CH2Cl2 (3:7) and the anion exchange was equally successful with both lipophilic cations and anions.

Azolium-based systems: application of an anion exchange resin (A- form) method and 1H NMR analysis of the charged-assisted (C–H)+•anion hydrogen bonds

“…15 However, when the recovery of the new ion pairs 2a·A or 2b·A was around 90%, further studies to increase the yield using a less polar solvent, for example acetonitrile, were not carried out. The prepared ion pairs were dried in a vacuum oven at 60 ºC in the presence of desiccant agents and their characterization was confirmed by spectroscopic and spectrometric methods, especially 1 H NMR, and when necessary unambiguous assignments were made by NOESY experiments at 400 MHz. Moreover, the amount of halide content was determined by a silver chromate test following a similar protocol to that described by Sheldon and co-workers.…”

“…1-buthyl-3-methylimidazolium salts 1a·A, 1 1-buthyl-3-methyltriazolium iodide 2a·I, 15 1-benzyl-3-methyltriazolium iodide 2b·I, 15 The amount of halide contents was determined by a silver chromate test following a similar protocol to that described by Sheldon and co-workers. 30 An aqueous solution (5 mL) of potassium chromate (5 % p/v in Milli-Q water, 0.257 M) was added to the sample (5-10 mg).…”

“…Application of the anion exchange resin (A¯ form) method in non-aqueous media to representative imidazolium-based ionic liquids 1·X. 1 A logical extension of our previous studies on imidazolium-based systems was to examine 1,3-dialkyl-1,2,3-triazolium 2·X, which have been described as stable and recyclable solvents. [15][16][17][18] The present study is focused on the application of the AER (A¯ form) method for the iodide-to-anion exchange of the selected triazolium ion pairs.…”

Investigations of structure property relationships of highly hygroscopic Imidazolium and Choline based ILs for the prediction of thermodynamic trends

“…[8][9][10][11][12][13][14] Subsequently the anion can be changed by an ion exchange column according to Alcalde et al (Chart 1). 15 To verify the completeness of the exchange we analyzed the NMR Spectra and do a silver test. The high purity of these procedure is evidenced by the crystal structures of the compounds 3, 7, 8, 12, 13, 19, 25-30.…”

Analyzing the solution behavior of hygroscopic Imidazolium and Choline based ILs for optimizing liquid sorption media

“…[5][6][7][8][9][10][11] Subsequently the anion can be changed by an ion exchange column according to Alcalde et al (Chart 1). 12 To verify the completeness of the exchange we analyzed the NMR Spectra and perform a silver test. The high purity of these procedure is evidenced by the crystal structures of the compounds 3, 7, 8, 12, 13, 19, 25-30.…”