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Issue 39, 2011
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Association of ionic liquids in solution: a combined dielectric and conductivity study of [bmim][Cl] in water and in acetonitrile

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Abstract

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.

Graphical abstract: Association of ionic liquids in solution: a combined dielectric and conductivity study of [bmim][Cl] in water and in acetonitrile

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Supplementary files

Article information


Submitted
29 Apr 2011
Accepted
01 Aug 2011
First published
05 Sep 2011

Phys. Chem. Chem. Phys., 2011,13, 17588-17598
Article type
Paper

Association of ionic liquids in solution: a combined dielectric and conductivity study of [bmim][Cl] in water and in acetonitrile

M. Bešter-Rogač, A. Stoppa, J. Hunger, G. Hefter and R. Buchner, Phys. Chem. Chem. Phys., 2011, 13, 17588
DOI: 10.1039/C1CP21371G

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