Electronic quantum fluxes during pericyclic reactions exemplified for the Cope rearrangement of semibullvalene.

The outcome of a pericyclic reaction is typically represented by arrows in the Lewis structure of the reactant, symbolizing the net electron transfer. Quantum simulations can be used to interpret these arrows in terms of electronic fluxes between neighboring bonds. The fluxes are decomposed into contributions from electrons in so-called pericyclic orbitals, which account for the mutation of the Lewis structure for the reactant into that for the product, in other valence and in core orbitals. Series of time-integrated fluxes of pericyclic electrons can be assigned to the arrows, for example 0.09-0.23 electrons for Cope rearrangement of semibullvalene, with hysteresis-type time evolutions for 27.3 fs. This means asynchronous electronic fluxes during synchronous rearrangement of all the nuclei. These predictions should become observable by emerging techniques of femto- to attosecond time-resolved spectroscopy.