Aromatization energy and strain energy of Buckminsterfullerene from homodesmotic reactions

Abstract

The amount of aromatic stabilization. of C-60 fullerene (E-aroma) and the amount a. its destabilizing strain effect (E-strain) are unknown quantities because both are intimately connected and difficult to separate. Based on experimentally known transformation Of C60H30 to C-60 and conversion of A polycyclic aromatic hydrocarbon C60H20 to the nonaromatic linear conjugated C60H62, new homodesmotic reaction schemes have been proposed to evaluate E-aroma and E-strain. The E-aroma values 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 E-strain values at these levels are 327.3, 382.0, and 381.4 kcal/mol, respectively. These data suggest that a CC bond of C-60 is destabilized by similar to 2.28-2.54 kcal/mol compared to that of benzene, and this minor energetic effect explains the existence of C-60 as a stable molecule.