The difference between B3LYP and M06-2X reaction energy is here only 1.5 and 1.9 kcal/mol with the CPCM and SMD solvation corrections, respectively. Together with the fact that the B3LYP calculations with CPCM reproduce both the experimentally known barrier and a reaction energy in agreement with the experimental reaction enthalpy, suggests that -13.2 kcal/mol is a sufficiently reliable estimate for ∆G0. Thus, this value was used further to calibrate the EVB reference reaction Hamiltonian.