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Quantum chemical study of the energetics and directionality of acid-catalyzed aromatic epoxide ring openings



Epoxide ring openings play important roles in a variety of chemical situations and are believed to be important in the metabolic processes through which some polycyclic aromatic hydrocarbons are converted to carcinogenic species. In this report, the energetics and directionalities of acid-catalyzed epoxide ring openings in benzene and naphthalene are examined using quantum chemical (MNDO/d and MP2/6-31G*) methods. In particular, the consequences of local saturations in the aromatic systems are examined and shown to exert strong influences on the resulting energetics and product distributions. Partial ring saturation in an aromatic system leads to barrier-free, spontaneous ring opening of the protonated epoxide in a favored direction and eliminates opening in the opposite direction. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010