Is universal, simple melting point prediction possible?
U. Preiss, W. Beichel, A. M. T. Erle, Y. U. Paulechka, I. Krossing.
ChemPhysChem, 12, 2959–2972, (2011)
An investigation of the melting points of 520 organic 1:1 salts is presented with the aim of developing a universal, simple, physically well-founded prediction scheme. The general reliability and reproducibility of the recorded experimental data are discussed with respect to purity, phase behavior, disorder and thermal history of a given substance. Additionally, mistakes, systematic errors, or lack of conventions can lead to considerable differences in the experimental measurements. A rough error bar for the reproducibility of the melting points of organic salts of ±5 to ±15 °C can be assigned. With this restraint, we developed two simple, semiempirical, five- and nine-parameter schemes with easy-to-calculate quantities. With these, we could predict the melting temperature of a given organic salt in the temperature range of −25 to +300 °C with an average error of 33.5 °C and a relative error of 9.3 %. All calculated quantities are assessed with the help of conventional DFT, COSMO and COSMO-RS calculations, and are currently implemented into the IL-Prop module of the upcoming version of COSMOtherm. These prediction schemes are suitable for high-throughput computational screening of substances in the context of “computer-aided synthesis”. Therefore, they are valuable tools to find a compound with a suitable melting point before its first synthesis.
Keyword(s): calorimetry; computational chemistry; ionic liquids; melting point; thermodynamics