Testing the Clar theory: Cyclic conjugation in some benzo- and naphthaleno-annelated ovalenes

Abstract

Cyclic conjugation (assessed by its energy effect) is studied in benzo- and naphthaleno-annelated ovalenes, in which annelation is in positions d and o. These benzenoid species possess a large number of Clar aromatic sextet formulas, making the application of Clar theory difficult and ambiguous. Some predictions based on Clar formulas are not in agreement with the calculated energy effects. This indicates that Clar theory is not universally applicable, even in the case of fully conjugated benzenoid molecules.