Predictions of solvation Gibbs free energies with COSMO-SAC approaches

The modelling of a detailed kinetics mechanism in the liquid phase is still not well understood, and the description of solvent effect on reaction rates remains a challenge. Green and co-workers proposed an approach to predict the kinetic constants in liquid phases, which is based on a correction of the kinetic constants in the gas phase. The correction term in Green's approach involves the solvation Gibbs free energies of the chemical species involved in the reactions. Examples of applications of the method are the kinetic modelling of the oxidation of liquid fuels or the catalytic pyrolysis of biomass. However, an accurate thermodynamic model is required to predict the solvation energies. In this work, several predictive models of solvation energies are compared to the large set of experimental data reported recently by Moine et al. [J. Phys. Chem. Ref. Data, 46, 2017] in the CompSol database. Activity coefficients and solvation Gibbs free energies were calculated with different versions of the COSMO-SAC thermodynamic model. We propose a re-optimisation of the universal parameters of these COSMO-SAC models, and extend them to CPCM cavities. It is found that these approaches are in general much more accurate than the Abraham solvation model that is usually employed in Green's approach.