Carcinogenicity of methylated hydrocarbons: effect of methylation on the calculated diol-epoxide reactivity

Methyl substitution of polycyclic aromatic hydrocarbons is known to induce substantial variations in carcinogenicity. The "Bay-region" theory relates carcinogenicity of polycyclic aromatic hydrocarbons to ease of formation of a triol carbocation from a bay-region diol-epoxide. It is shown that an examination of certain simple consequences of molecular orbital theory enables one to identify certain methyl substitutions that do not enhance ease of carbocation formation and hence are the least carcinogenically activating.