ABSTRACT
The aromaticity is an extra stability which aromatic molecules have in comparison with reference non-aromatic molecules. Although aromaticity is associated to a huge increase in the stability of the aromatic compound in comparison with a corresponding non-aromatic compound, the reason for this high stability is still in debate and perhaps will never reach a consensus. Aromaticity can also be estimated from the delocalization energy, which is the energy difference between the resonance hybrid and its most stable resonance structure. Benzene is the iconic example of an aromatic compound being the most aromatic of the benzenoid series. There are four criteria associated with aromaticity: geometric, energetic, electronic, and magnetic. The electronic criterion of aromaticity arises from Huckel’s work, known as Huckel method or Huckel Molecular Orbital. In the case of homoaromatic systems, the degree of degeneracy was empirically obtained so that the influence of heteroatoms in the aromatic circuit could be taken into account for evaluating the homoaromaticity.
