Bullvalene

This is a short post based on a J Chem Ed article, describing a remarkable hydrocarbon in permanent flux. Figure: The structural formula of bullvalene - every single carbon atom in the structure will interchange with every other atom at room temperature.

Bullvalene

A glance at a line drawing of a molecule might give the impression that molecules are sedate entities, calming drifting through the microscopic world. Molecules are in reality very lively, perpetually vibrating, tumbling and bouncing off each other. Despite all this motion, bonds in molecules remain intact, as the energy needed to break them is so much larger than the energy of a molecule at room temperature.

William Doering and Wolfgang Roth noticed however, that if a molecule had a double bond next but one to a C-C bond, the energy needed to break that bond was lowered significantly. If that C-C bond is also included in a three membered ring, the strain weakens the bond even further. Doering and Roth designed a molecule, ‘bullvalene’ – a pun on Doering’s nickname of Bull and his usual research area of fulvalenes – that combined these features to lower the bond energy of the C-C bond so much that the predicted it could break at room temperature. Further, the cage-like structure of bullvalene would mean that instead of falling apart, a new bond would form, giving the net effect of swapping the positions of two carbon atoms. In effect, all the carbon atoms in bullvalene would swap positions constantly, despite bullvalene being a simple hydrocarbon. Even more remarkably, their predictions were completely correct – when the molecule was made the next year, it showed everything that Doering and Roth had predicted. Bullvalene may not be useful – but it is a remarkable molecule and demonstration of the success of physical organic chemistry.