Racemization and singlet-triplet energy gaps in cyclic divalent seven-membered C6H6C and its heavier analogues

Aromatic character is not a directly measurable or computable quantity. Aromatic character is generally evaluated on the basis of energetic, geometric, and magnetic criteria [1-6]. There is some procedure for the estimation of aromatic stabilization energies (ASE) and/or homo-aromatic stabilization energies (HASE) from various isodesmic reactions [7]. These usually require comparisons the nonaromatic model compounds respect to aromatic model compound. Isodesmic reaction schemes insist only equal numbers of formal single and double bonds in products and reactants. Systems with negative SE are aromatic, while those with positive ASE are antiaromatic.