Abstract
The electrical conductances of very dilute solutions of the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate [emim][BF4] and 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] in the low-permittivity solvent dichloromethane have been measured in the temperature range from 278.15 to 303.15 K at 5 K intervals. The data was analyzed assuming the possible presence of contact (CIP) and solvent-separated (SSIP) ion pairs in the solution on the basis of lcCM model to obtain ionic association constants, K A, and the limiting molar conductivities, Λo, of these electrolytes. The examined ionic liquids are strongly associated in dichloromethane over the whole temperature range. From the temperature dependence of the limiting molar conductivities, the Eyring’s activation enthalpy of charge transport was determined. The thermodynamic functions such as Gibbs energy, entropy, and enthalpy of the process of ion pair formation were calculated from the temperature dependence of the association constants.
Highlights
Creating sets of data on physical and chemical properties of ionic liquids (ILs) are of essential significance for both pure scientific and industrial purposes
We calculated the values of R independently, assuming the possible existence of contact (CIP) and solvent-separated (SSIP) ion pairs in the solution
Molar conductivities of very dilute solutions of 1-ethyl-3methylimidazolium tetrafluoroborate and 1-butyl-3methylimidazolium tetrafluoroborate in dichloromethane have been reported for the first time at T = 278.15 to 303.15 K
Summary
Creating sets of data on physical and chemical properties of ionic liquids (ILs) are of essential significance for both pure scientific and industrial purposes. The transport properties of According to our knowledge, conductometric data for solutions of [emim][BF4] and [bmim][BF4] in dichloromethane (DCM) at various temperatures have not yet been reported. The only paper is by Katsuda et al [11], who investigated the conductance of [bmim][BF4] in DCM exclusively at 298.15 K. Aiming to cover this topic, the present work deals with the precise conductivity measurements, which have been carried out in the concentration range c = 0.4 to 4 · 10−4 mol · dm−3 of [emim][BF4] and [bmim][BF4] in DCM at temperatures range 278.15–303.15 K at atmospheric pressure. The obtained data were used to calculate the values of the limiting molar conductivities, Λo, Ionics (2016) 22:859–867
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