BUCKMINSTERFULLERANE - THE INSIDE STORY

The stereoisomers of fully reduced buckminsterfullerene C60H60 have been investigated with the molecular mechanics program MM3. Although it might be expected that chemical reduction would deliver all of die hydrogens to the outside, the symmetric structure produced in this way is predicted to be highly strained. Moving just one hydrogen to the inside is predicted to decrease the energy by 53 kilocalories (kcal) per mole. Putting additional hydrogens on the inside further lowers the predicted energy (depending on the steric relations between them). The minimum energy isomer is predicted to have ten hydrogens inside with C1 symmetry and to have an energy 400 kcal/mol less than that of the all-outside isomer. These results suggest that a process which could achieve isomerization would produce a mixture of isomers, most of which with ten hydrogens on the inside.