(257ac) A QSPR Approach for Accessing the Heat Capacity of Solidified Ionic Liquids

Ionic Liquids (IL) are low melting salts that show properties that make them highly interesting for applications in many fields of chemical engineering. However, due to their Ionic nature they are quite often close to their melting point. In practical applications they often occur in their solidified form. Hence, it is insufficient just to know about their properties in the liquid state. One very important property is the heat capacity, but experimental data for ILs are often missing. For ILs in the liquid phase methods for the prediction of heat capacities are already available. ^[1] However, for the solid phase a reliable and simple prediction method is still missing.

In this contribution a Quantitative Structure Property Relationship (QSPR) based on first-order group contributions is presented. Based on the chemical structure of the ions constituting the IL it is possible to estimate the temperature depending heat capacity of solidified ionic liquids. The model has been evaluated by a test set of data not used for the model development. This data set contained 168 data points and is supposed to allow for a reliable conclusion on the actual quality of the proposed method.

The method was evaluated concerning its predictivity. Using the developed method it was possible to determine the heat capacity of solidified ILs with a relative error of 2.8 % for data points from the training set and 8.2 % data points from the test set.

^{[1]     Albert, J. and K. Müller, A Group Contribution Method for the Thermal Properties of Ionic Liquids. Industrial & Engineering Chemistry Research, 2014. 53(44): p. 17522-17526.}