I left the story of the molecule below on the precipice of a cliff. I had shaved off the four benzo groups (blue) in the time honoured computational tradition of clearing away distractions. Unfortunately, it became clear as the story unfolded that the benzo groups had a distractingly critical role to play, and so its time to start adding them back again, but in stages.
To recapitulate, this reaction (with four benzo groups) has a half life of ~30 minutes at 353K, giving it a a free energy barrier of ~26.2 kcal/mol. According to Woodward and Hoffmann, it is a “forbidden” reaction (4n, n=2, electrons require an antarafacial component from somewhere). Shorn of the benzo groups, such a component developed in one of the forming phenyl rings (forming a Möbius benzene). But, by adding two benzo groups back to this phenyl ring (turning it into an anthracene), we will stop this process in its tracks. (more…)