Unraveling the Bonding Nature Along the Photochemically Activated Paterno‐Büchi Reaction Mechanism
Cristian Guerra, Leandro Ayarde‐Henríquez, Mario Duque‐Noreña, Eduardo Chamorro
Abstract
Abstract The photochemically activated Paterno‐Büchi reaction mechanism following the singlet excited‐state reaction path was analyzed based on a bonding evolution framework. The electronic rearrangements, which describe the mechanism of oxetane formation via carbon‐oxygen attack (C−O), comprises of the electronic activation of formaldehyde and accumulation of pairing density on the O once the reaction system is approaching the conical intersection point. Our theoretical evidence based on the ELF topology shows that the C−O bond is formed in the ground‐state surface (via C−O attack) returning from the S 1 surface accompanied by 1,4‐singlet diradical formation. Subsequently, the reaction center is fully activated near the transition state (TS), and the ring‐closure (yielding oxetane) involves the C−C bond formation after the TS. For the carbon‐carbon attack (C−C), both reactants (formaldehyde and ethylene) are activated, leading to C−C bond formation in the S 1 excited state before reaching the conical intersection region. Finally, the C−O formation occurs in the ground‐state surface, resulting from the pair density flowing primarily from the C to O atom.