NMR Diffusion Measurements as a Simple Method to Examine Solvent–Solvent and Solvent–Solute Interactions in Mixtures of the Ionic Liquid [Bmim][N(SO₂CF₃)₂] and Acetonitrile

Abstract

The self-diffusion coefficients of each component in mixtures of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim][N(SO CF ) ]) and acetonitrile were determined. The results suggest that the hydrodynamic boundary conditions change from "stick" to "slip" as the solvent composition transitions from "ionic liquid dissolved in acetonitrile" (χ <0.4) to "acetonitrile dissolved in ionic liquid" (χ >0.4). At higher χ , the acetonitrile species are affected by "cage" and "jump" events, as the acetonitrile molecules reside nearer to the charged centre on the ions than in the "non-polar" regions. The self-diffusion coefficients of hexan-1-amine, dipropylamine, 1-hexanol and dipropylether in mixtures of [Bmim][N(SO CF ) ] and acetonitrile were determined. In general, the nitrogen-containing solutes were found to diffuse slower than the oxygen-containing solutes; this indicates that there are greater ionic liquid-N interactions than ionic liquid-O interactions. This work demonstrates that the self-diffusion coefficients of species can provide valuable information about solvent-solvent and solvent-solute interactions in mixtures containing an ionic liquid.

Ionic Liquids as Solvents for SN2 Processes. Demonstration of the Complex Interplay of Interactions Resulting in the Observed Solvent Effects

“…For example, while the viscosity of the mixture will change, and as a result diffusion of solutes will change, [24] the reactions are not under diffusion control so this does not affect the rate constants. The bimolecular nucleophilic substitution reaction between triphenylphosphine 5 and each of the benzyl derivatives 2, 6-8 to give the corresponding salts 9-12, which have been examined in reaction mixtures containing the ionic liquid 4 (a R=3,5-Me-4-MeO, b R=MeO, c R=Me, d R=H, e R=Br, f R=CF 3 , g R=NO 2 ).…”

Diffusion, Ion Pairing and Aggregation in 1‐Ethyl‐3‐Methylimidazolium‐Based Ionic Liquids Studied by 1H and 19F PFG NMR: Effect of Temperature, Anion and Glucose Dissolution

“…[15] in order to evaluatet he effect of cation and anion structure on the solvation mechanism. Their results showedt hat changes in the relaxation times of 13 Cn uclei of the imidazolium cation as af unctiono fc arbohydrate concentration weres mall compared to the changesi n 35/37 Cl and 13 C relaxation rates of chloride anions and acetate anion carbons, respectively.T his suggestst hat the dissolution processi sp redominantly governed by the interactions between the ionic liquid aniona nd the carbohydrate. Self-diffusion studies of the same systems revealed that in 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), the larger imidazolium cation, [EMIM] + , diffusesf aster than the smaller acetate anion, [OAc] À .T his behaviour suggestst hat the anions do not diffuse as isolated speciesbut as ap art of larger ion aggregates.…”

“…Therefore, also in the context of ionic liquids, PFG NMR measurements may represent a very powerful tool to investigate ion pairing. In addition, Keaveney et al . have shown that this method is also useful in understanding solvent‐solvent and solvent‐solute interactions in ionic liquids, suggesting that at high ionic liquid concentrations solvent molecules diffuse in a “cage” and “jump” fashion.…”

“…[12] Therefore, also in the context of ionic liquids, PFG NMR measurements mayr epresentavery powerful tool to investigate ion pairing. In addition, Keaveney et al [13] have shown that this method is also useful in understandings olvent-solventa nd solvent-solute interactions in ionic liquids, suggesting that at high ionic liquid concentrations solventm olecules diffuse in a" cage" and" jump" fashion. Ar ecent work by Price et al [14] has also used PFG NMR to understandi onic mobility in the 1-ethyl-3-methylimidazolium tricyanomethanide (EMIMTCM) ionic liquid.…”

The Dependence of Ionic Liquid Solvent Effects on the Nucleophilic Heteroatom in SNAr Reactions. Highlighting the Potential for Control of Selectivity

“…Additional details for the kinetic analyses including temperatures, rate constants, equations used to determine the rate constants and composition of stock solutions (masses, concentrations of reagents and mole fraction of ionic liquid), rate equations and derivations can be found in the Supporting Information. [29] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57…”