Association of ionic liquids in solution: a combined dielectric and conductivity study of [bmim][Cl] in water and in acetonitrile
Bešter-Rogač, M., Stoppa, A., Hunger, J., Hefter, G. and Buchner, R. (2011) Association of ionic liquids in solution: a combined dielectric and conductivity study of [bmim][Cl] in water and in acetonitrile. Physical Chemistry Chemical Physics, 13 (39). p. 17588.
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Ion association of the ionic liquid [bmim][Cl] in acetonitrile and in water was studied by dielectric spectroscopy for salt concentrations c ≤ 1.3 M at 298.15 K and by measurement of molar electrical conductivities, Λ, of dilute solutions (c ≤ 0.006 M) in the temperature range 273.15 ≲ T/K ≤ 313.15. Whilst acetonitrile solutions of [bmim][Cl] exhibit moderate ion pairing, with an association constant of KoA ≈ 60 M-1 and increasing with temperature, [bmim][Cl] is only weakly associated in water (KoA ≈ 6 M-1) and ion pairing decreases with rising temperature. Only contact ion pairs were detected in both solvents. Standard-state enthalpy, entropy and heat capacity changes of ion association were derived, as well as the activation enthalpy of charge transport and the limiting conductivity of the cation, λ∞([bmim]+). These data, in conjunction with effective solvation numbers obtained from the dielectric spectra, suggest that the solvation of [bmim]+ is much weaker in water than in acetonitrile.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Chemical and Mathematical Science|
|Publisher:||Royal Society of Chemistry|
|Copyright:||© Royal Society of Chemistry|
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