Calculated Energies, Reaction Paths and Transition States of C-H Bond Cleavage in the Aromatic Molecules

Density Functional calculations, of the B3LYP type and (6-31G), as well as (6-311G)Gaussian basis sets, for the reaction paths of the aromatic C-H bond cleavage in 2- to 4- (sixmembered ring) aromatic hydrocarbons reveal that, the calculated reaction energies are nearlysimilar to that of the unsubstituted benzene molecule (118.34kcal/mol). The calculated activation energies of the same reactions are also near that of benzene (169.46kcal/mol), with the exceptions of the C1-H1 and C9-H9 bonds in anthracene, where interaction with the neighbored H atoms is noticed. The calculated activation energies for these two bonds are (147.44kcal/mol) for C1-H1 and (154.00kcal/mol) for C9-H9. The departure of the H atom from the aromatic moiety proceeds coplanarily, i.e., in the same plane of the molecule. It causes a shortening of the C-C bond lengths at the reaction center and a reorientation of the C-C bonds in the aromatic ring forming successive bond alternation.