Prediction of free energies of hydration with COSMO-RS on the SAMPL3 data set

The COSMO-RS method has been used for the prediction of free energies of hydration on the dataset of 36 chlorinated ethanes, biphenyls and dioxins considered in the SAMPL3 challenge. Straight application of the latest version of the COSMOtherm software yields an overall predictive accuracy of 1.05 kcal/mol (RMSE). The predictions for the chlorinated ethanes and dioxins are much better with 0.40 and 0.49 kcal/mol RMSE, respectively. The predictions for the chlorinated biphenyls show a systematic shift of approximately 1 kcal/mol, but the large RMSE of 1.59 kcal/mol mainly arises from two exceptional outliers. Possible reasons for this observation are discussed.