Prediction of the free energy of hydration of a challenging set of pesticide-like compounds.

In a blind validation test the COSMO-RS method, a combination of the quantum chemical dielectric continuum solvation model COSMO with a statistical thermodynamics treatment for more realistic solvation (RS) simulations, has been used for the direct prediction of transfer free energies of 55 demanding pesticide-like compounds. Comparison with experimental data yields an rms deviation of approximately 2 kcal/mol, which is in the order of the estimated inaccuracy of the experimental data. A detailed comparison reveals experimental and calculation pitfalls on conformational flexible, multifunctional, polar compounds.