The Aromatic Sextet and its Significance in Relation to the Stability of Aromatic Systems

Abstract

Soon after Kekulé published his benzene formula certain difficulties arose. According to this formula two isomeric o-disubstituted deriva­tives should be formed, but these have not been found. In fact benzene shows hexagonal and not trigonal symmetry. Similarly, two different annellation products must be formed if benzene contains three double bonds.