Supporting Information: The role of methyl–induced polarization in ion binding

In Table S1, the computational estimates are obtained as follows. The reactant and product molecular configurations are first relaxed separately at the PBE+vdW level of theory [1], using the all-electron program package FHI-aims [2]. We used tight settings for the numeric atom centered orbitals basis sets and integration grids, as explained in Ref. [2]. Following relaxation, the complex geometries are subjected to a single point calculation using the hybrid PBE0[3, 4]+vdW functional, which yields their electronic energies E . The Gibbs free energy of each complex is then estimated using the ideal gas thermodynamic relationship, G = F +kBT , where kB is the Boltzmann constant, T = 298 K, and F is the Helmholtz free energy. Assuming that the coupling between translational, vibrational and rotational degrees of freedom can be neglected, F is estimated as a sum of their independent contributions [5], that is, F = Ftrans + Fvib + Frot, where