Fifty-six years after the concept of pericyclic reactions was created by Woodward and Hoffmann, more intricacies about the transition states of pericyclic reactions are being discovered. Many studies of the competition between concerted and stepwise mechanisms led Doering to propose the concept of “energy of concert” – the difference in energy between concerted and stepwise reactions. In 1992, we published a review on the transition states that were located by quantum mechanical calculations available at the time – mainly Hartree-Fock and MP2, before DFT was commonly used for organic reactions.  Since that time, more accurate calculations have become common, and ambimodal pericyclic transition states, first discovered computationally by Caramella, have been shown to be common for higher-order cycloadditions, leading to multiple products. More quantitative energies of concert have been established, along with a tiny subset of reactions that violate the Woodward-Hoffmann rules (“Violations? There are none.”). Recent discoveries from our laboratories about pericyclic transition states and energies of concert will be described.

Pericyclic transition states and energies of concert

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.