Temperature-dependent prediction of the liquid entropy of ionic liquids.

Modeling of the temperature-dependent liquid entropy of ionic liquids (ILs) with great accuracy using COSMO-RS is demonstrated. The minimum structures of eight IL ion pairs are investigated and the entropy, calculated from ion pairs, is found to differ on average only 2% from the available experimental values (119 data points). For calculations with single ions, the average error amounts to 2.6% and stronger-coordinating ions tend to give higher deviations. Additionally, the first parameterization of the standard liquid entropy for ILs is presented in the context of traditional volume-based thermodynamics (S(l)(0)=1.585 kJ mol(-1) K(-1) nm(-3)·r(m)(3)+14.09 J mol(-1) K(-1)), which sheds light on the statistical treatment of ionic interactions. The findings provide the first direct access to accurate predictions of liquid entropies of ILs, which are tedious and time-consuming to measure.