Tetrahydrothiophene-Based Ionic Liquids: Synthesis and Thermodynamic Characterizations.

S-alkyltetrahydrothiophenium, [C THT] bis(trifluorosulfonyl)imide, [NTf ] room temperature ionic liquids (ILs) and tetraphenylborate, [BPh ] salts with alkyl chain lengths from C to C have been prepared. The ILs and salts were characterized and their purity verified by H- and C-nuclear magnetic resonance, elemental analysis, ion chromatography, Karl-Fischer titration, single crystal X-ray diffraction as well as thermogravimetric analysis. The experimentally determined density and viscosity decrease with increasing temperature. The experimental solubility of the [C THT][NTf ]-ILs in water (75 to 2.2 mg/L for C to C ) was modelled with very good agreement by Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT), based on the extremely low vapor pressures for the [C THT][NTf ]-ILs measured in this work (4.15 to 0.037 ⋅ 10 ×p for C to C ). PC-SAFT is able to predict and correlate different thermodynamic properties by estimating the Helmholtz residual energy.