Coupling Quantum Interpretative Techniques: Another Look at Chemical Mechanisms in Organic Reactions

A cross ELF/NCI analysis is tested over prototypical organic reactions. The synergetic use of ELF and NCI enables the understanding of reaction mechanisms since each method can respectively identify regions of strong and weak electron pairing. Chemically intuitive results are recovered and enriched by the identification of new features. Noncovalent interactions are found to foresee the evolution of the reaction from the initial steps. Within NCI, no topological catastrophe is observed as changes are continuous to such an extent that future reaction steps can be predicted from the evolution of the initial NCI critical points. Indeed, strong convergences through the reaction paths between ELF and NCI critical points enable identification of key interactions at the origin of the bond formation. VIVID scripts enabling the automatic generation of movies depicting the cross NCI/ELF analysis along a reaction path (or following a Born-Oppenheimer molecular dynamics trajectory) are provided as Supporting Information.