TESTING THE Y–RULE IN CLAR THEORY

Abstract

A recently proposed modification of the basic postulates of the Clar aromatic sextet theory, called the Y–rule, is tested on a suitably chosen homologous series of benzenoid hydrocarbons. For these benzenoid systems the original Clar theory predicts a significantly different distribution of π-electrons than the Y–rule. It was found that both the π-electron contents of rings as well as their energy effects agree with the predictions of the original Clar theory, failing to corroborate the Y–rule.