Topological description of complex patterns of bonding, charge transference and structural changes in chemical reactions: S2 type reactions, a case study.

In this report we deeply explore the electron rearrangements for a chemical reaction case study of the SN2 type OH- + CH3-CN ↔ HO-CH3 + CN-, within the topological formalism of QTAIM model in its local and the non-local or integrated form implementations. This is part of our main interest of a subtle description of the electron distribution at both, equilibrium and non-equilibrium conformations for the state function at correlated level of approximation. The emphasis is mainly placed on the determination of complex patterns of interaction of two or four electrons in three centers (2e-3c, 4e-3c). These results confirm them as a measure of electron excess or electron deficiency effects and revels their crucial importance in the charge transference process and its relationship with these complex patterns. All electronic magnitudes were followed along the configurations from reactants to products passing through the corresponding transition state TS. The results obtained throughout this case study reveals the high performance of the topological formalism of Bader type in the subtle description of electron rearrangements in a chemical transformation.