Discussion on Electronic Activity and Molecular Activation Processes in Chemical Reactions

Activation processes have been studied in many different contexts, in this lecture we will discuss two essential aspects: energetic and electronic. Among many theoretical models intended to rationalize chemical processes and the energies involved, the Marcus equation is one of the most successful analytic forms that provides nice ways to rationalize the activation energy and to characterize the transition state through the Hammond postulate and the Brönsted coefficient. The Marcus’ equation involves the reaction energy and the so-called Marcus’ intrinsic activation energy that describes structural distorsion of reactants and products at the transition state. An analytic potential function consistent with the Marcus equation for activation energy, is formulated and used to reveal new insights on activation processes in chemical reactions. Moreover, since the parameters necessary to define this new potential energy function can be obtained experimentally, the present model may produce experimental analytic potentials allowing for new and interesting applications and emerging as a powerful tool to characterize activation processes in chemical reactions. On the other hand, activation processes usually involve intense electronic activity resulting in bond cleavage and/or formation. In this context he reaction electronic flux, a descriptor of the electronic activity taking place along a reaction coordinate, has proven to be quite adequate to elucidate the mechanism of complex reactions. Few chemical reactions are visited and analysed in the light of the above mentioned ideas.