A theoretical—information study on the electron delocalization (aromaticity) of annulenes with and without bond alternation

Abstract

Using the recently developed theoretical—information approach to electron delocalization (aromaticity) within the HMO approximation, analytical expressions have been obtained for the information content (aromaticity index) of 4 n and (4 n + 2) annulenes with and without bond alternation. The information function proves to be sensitive to the size and symmetry of annulenes, reflecting correctly the aromatic, antiaromatic and non-aromatic behaviour of the various annulenes. A high correlation is found between the information index and other aromaticity indices such as the Hess and Shaad resonance energy, the topological resonance energy of Trinajstić and Aihara, the Dewar resonance energy, etc., as well as with the Sondheimer rate constants for the formation of annulenes.