Steric crowding can stabilize a labile molecule: solving the hexaphenylethane riddle.

12 not so angry men: Hexaphenylethane is unstable, a phenomenon traditionally attributed to steric repulsion between the six phenyl rings. However, adding 12 bulky tert-butyl groups, one to each of the 12 meta positions, gives a stabile ethane derivative (see space-filling model and potential energy curve for the dissociation of the central C-C bond). This unexpected stabilization is shown to result from attractive dispersion interactions between the substituents.