Bond formation insights into the Diels–Alder reaction : A bond perception and self-interaction perspective

The behavior of electrons during bond formation and breaking cannot commonly be accessed from experiments. Thus, bond perception is often based on chemical intuition or rule-based algorithms. Utilizing computational chemistry methods, we present intrinsic bond descriptors for the Diels–Alder reaction, allowing for an automatic bond perception. We show that these bond descriptors are available from localized orbitals and self-interaction correction calculations, e.g., from Fermi-orbital descriptors. The proposed descriptors allow a sparse, simple, and educational inspection of the Diels–Alder reaction from an electronic perspective. We demonstrate that bond descriptors deliver a simple
visual representation of the concerted bond formation and bond breaking, which agrees with Lewis’ theory of bonding.