Heteroatom effects in chemical carcinogenesis: effects of ring heteroatoms on ease of carbocation formation.
The presence of a heteroatom can influence the ease with which a PAH diol-epoxide forms a triol carbocation. The influence of the heteroatom should be greatest when it is located where the PAH undergoes maximum charge change upon ionization. Extended Hückel, INDO and Gaussian 70 calculations on nitrogen substituted benz[a]anthracene verify this reasoning. The sites of maximum effect are easily predicted using a simple Hückel method which does not require use of a computer. The greater carcinogenic activity of methylated benz[c]acridines over benz[a]acridines is an immediate result of these considerations. Methylated benzo[c]phenarsazines are implicated as likely carcinogens.更多