A simple mathematical model for the effect of benzo-annelation on cyclic conjugation.

In a series of earlier studies, it was established that benzo-annelation in the angular (resp. linear) position relative to a ring R of a polycyclic conjugated π- electron system, increases (resp. decreases) the intensity of the cyclic conjugation in the ring R. Herein, it is shown how this regularity can be explained by means of a simple, Kekulé;-structure-based argument, itself based on an idea of Randić from the 1970s. [ABSTRACT FROM AUTHOR]