Secondary and Multiple Additions

For aU reactions on the fullerene, not only the stoichiometry, but also the regi-ochemical course of possible multiple reactions has to be considered. In principle, derivatives of with 60 addends are conceivable, which would mean complete saturation of the carbon core. Still for the time being molecules like that have not 

For the compounds generated, the degree of functionalization is governed by different factors. Firstly, the preparation of modestly functionalized species can only succeed with a sufficiently low amount of reactand, and secondly, the number of possible addition steps is limited by the steric and electronic conditions in the fuUerene. With bulky addends, for example, a much lower number of addition steps is possible than with smaller residues. With the degree of functionalization increasing, the remaining six-membered rings more and more resemble benzene, which finally causes the addition of further reactand molecules to cease. 

In reality, however, not all of these isomers are found in the respective second additions, and others are particularly frequent Which ones these might be depends on the kind of addends. Provided they are very small, like, for example, hydrogen atoms, the second addition of another H 2-molecule takes place in ds-1-position. For larger addends, an attack at this site is impossible due to steric repulsion. In these cases, the equatorial isomers are found preferably, besides certain amounts of the trans-3-isomer. 

An even larger number of isomers is conceivable if the formation of (5,6)-adducts is included in the considerations on possible regioisomers. These can no longer be described with the nomenclature of secondary addition outlmed 

Echegoyen, F. Diederich, L. E. Echegoyen. Bearochemistry of Fullerenes, in K. M. Radish, R. S. Ruoff (editors). Fullerenes, Wiley 

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