Investigation of the possibility of functionalization of C20 fullerene by benzene via Diels–Alder reaction

• In some of the recent researches, the possibility of Diels–Alder reaction between C60 fullerene and the central ring of anthracene was reported, and it proved that aromatic π-bonds could be reactive in some especial cases. In this project, due to non-spherical aromatic character, relative instability of C20 fullerene compared to bigger fullerene family, and the ability of this molecule in making ultra-fast Diels–Alder reaction with 1,3-butadiene, we have examined the possibility the Diels–Alder reaction of this small carbon cage (as dienophile) and benzene (as diene), and vice versa.
• The results show that at least in the case of C20 fullerene and benzene, the [4+2] Diels–Alder cycloaddition could occur with a rate constant of 7.424(10−4) s−1 due to its ∆G0,# (21.72 kcal mol−1). And it is near to the rate constant of Diels–Alder cycloaddition of C60 fullerene and the central ring of anthracene (4.28(103) s−1 in toluene as solvent, at 40 °C) which was reported previously.
• It is tried to consider all of the possible reaction channels.

C20 fullerene, this novel species with all its pentagonal faces has displayed some unique operations in making fast pericyclic reactions. As an example, the high dienophile character of the C20 fullerene and the ability of this species in making an ultra-fast Diels–Alder reaction with 1,3-butadiene, has been recently reported. Moreover, new experimental reports claim that the C60 fullerene, one of the fullerene family, could make a Diels–Alder reaction with the central ring of anthracene and make the ring non-aromatic. These reports may encourage researchers to do more studies on the properties of this small carbon cage.To address this question, the present research has discussed all the reaction channels of the Diels–Alder cycloaddition of benzene molecule as a 1,3-diene with the C20 fullerene in order to answer this question: “Is C20fullerene able to make a Diels–Alder reaction with this molecule?”.

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