C60 bearing ethylene moieties

The reactive sites in [4+2] cycloadditions to C60 are discussed based on vibronic coupling density (VCD) for the reaction mode. The frontier orbital theory encounters difficulty to predict reactive sites for such a large system, because of the delocalization of the frontier orbitals. The VCD analysis clearly illustrates the existence of ethylene moieties embedded in the C60 cage which behaves as a dienophile. The C60 cage contains six isolated double bonds as a functional group. The VCD for the reaction mode can be regarded as a reactivity index.