Aromatization Energy and Strain Energy of Buckminsterfullerenefrom Homodesmotic Reactions.

The amount of aromatic stabilizationof C60fullerene(Earoma) and the amount of its destabilizingstrain effect (Estrain) are unknown quantitiesbecause both are intimately connected and difficult to separate. Basedon experimentally known transformation of C60H30to C60and conversion of a polycyclic aromatic hydrocarbonC60H20to the nonaromatic linear conjugatedC60H62, new homodesmotic reaction schemes havebeen proposed to evaluate Earomaand Estrain. The Earomavalues obtained at M06L/6-311G(d,p), M062X/6-311G(d,p), and B3LYP-D3/6-311G(d,p)levels of density functional theory are 122.3, 169.8, and 152.4 kcal/mol,respectively, whereas Estrainvalues atthese levels are 327.3, 382.0, and 381.4 kcal/mol, respectively. Thesedata suggest that a CC bond of C60is destabilized by ∼2.28–2.54kcal/mol compared to that of benzene, and this minor energetic effectexplains the existence of C60as a stable molecule. [ABSTRACT FROM AUTHOR]