Thermodynamic properties of the N-octylquinolinium bis{(trifluoromethyl)sulfonyl}imide

This work is a continuation of our wide ranging investigation on quinolinium based ionic liquids (ILs). The study includes specific basic characterisation of the synthesized compounds N-octylquinolinium bromide, [OQuin][Br] and N-octylquinolinium bis{(trifluoromethyl)sulfonyl}imide [OQuin][NTf2] by NMR spectra, elementary analysis and water content. Differential scanning calorimetry (DSC) measurements gave us properties of the pure [OQuin][NTf2] i.e. melting and glass-transition temperatures, the enthalpy of fusion as well as heat capacity at the glass transition. Densities and viscosities were determined as a function of temperature. The temperature-composition phase diagrams of 10 binary mixtures composed of organic solvent dissolved in the IL: {[OQuin][NTf2] + aromatic hydrocarbon (benzene, or thiophene, or toluene, or ethylbenzene, or n-propylbenzene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol, or 1-dodecanol)} were measured at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (250 to 370) K. For mixtures with benzene and alkylbenzenes, the immiscibility gap in the liquid phase in a low mole fraction of the IL was observed with upper critical solution temperature (UCST) higher than the boiling point of the solvent. In the system with thiophene, the immiscibility gap is lower and UCST was measured. For binary mixtures with alcohols, complete miscibility in the liquid phase was observed for 1-butanol and 1-hexanol. In the systems with longer chain alcohols, the immiscibility gap with UCST was noted. Typical behaviour for ILs was observed with an increase of the chain length of an alcohol the solubility decreases. The well-known NRTL equation was used to correlate experimental (solid + liquid), SLE and (liquid + liquid), LLE phase equilibrium data sets.