Local Density Functional Electronic Structures of Three Stable Icosahedral Fullerenes

a distinctive and general feature of gas-phase aromatic substitution, occurs only in those cases where the electrophile fulfils certain requirements. Paramount among the latter seem to be the presence of H atoms carrying a substantial fraction of the positive charge, capable of establishing localized H bonds with the unshared electrons of the substituent, as well as a suitable geometry of the cation, allowing simultaneous interaction with the n-type and the *-type nucleophilic centers of the bidentate substrate, and finally the lack of steric hindrance to ortho substitution. All such features characterize to a comparable extent i-C3H7+ and (CH3)2F+, the two gaseous reactants that consistently give the highest extent of substitution ortho to groups containing unshared electron pairs.