On the distribution of π-electrons into rings of conjugated hydrocarbons containing a linear polyacene fragment

A method for assessing the pi-electron contents (EC) of rings of benzenoid hydrocarbons, based on the examination of their Kekule structures, was recently put forward by Balaban and Randic. We now show that all hexagons belonging to a linear polyacene fragment of a conjugated hydrocarbon (not necessarily benzenoid) have mutually equal EC-values.