Abstract
Since Kekulé's discovery of the benzene structure, chemists have been seeking a generally acceptable definition of aromatic stabilization. Their efforts resulted in a variety of ideas and indexes concerning aromatic chemistry. Most of them, however, failed even to attribute aromaticity to cyclic π-electron conjugation. Some indexes have shared the name “resonance energy”. Dewar defined in 1965 what is called Dewar-type resopance energy. It was epoch-making, in that an aromatic compound was characterized reasonably by its positive value. The absence of double-bond reactivity in an aromatic compound was then associated with an extra thermodynamic stability inherent in such a cyclic π-electron system. We devised a graph theory of aromaticity in 1975, and succeeded in explaining many physicochemical aspects of an aromatic compound within a single theoretical framework. This theory enabled us to evaluate Dewar-type resonance energy with no fitting of parameters.
