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COMPARISON OF QUANTUM MECHANICAL METHODS TO COMPUTE THE BIOLOGICALLY RELEVANT REACTIVITIES OF CYCLOPENTA POLYCYCLIC AROMATIC HYDROCARBONS
Citation:
Rabinowitz, J. AND S. Little. COMPARISON OF QUANTUM MECHANICAL METHODS TO COMPUTE THE BIOLOGICALLY RELEVANT REACTIVITIES OF CYCLOPENTA POLYCYCLIC AROMATIC HYDROCARBONS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/044, 1994.
Description:
In computational studies to understand the interaction of polycyclic aromatic hydrocarbons (PAHS) with biomolecular systems, the semi-empirical method AM1 has been used to determine the geometry of the PAH, its metabolites and relevant intermediates. umber of studies have shown that AMI provides geometries for parent PAHs that are acceptably close to experimentally determined structures. owever, many of the properties that determine the manner by which PAHs interact with biological nucleophiles depend on the structure of metabolites and reactive intermediates where less experimental information is available. n a previous study, we had used AM1 to obtain the molecular geometries of reactive intermediates of cyclopenta-PAHs (cPAHs) and then used single point Hartree-Fock calculations, with the Gaussian 3-21g basis set, to obtain molecular,energies and charge distributions, in order to predict the direction of epoxide ring opening. ecent advances in the availability of computational hardware and software have provided other, more rigorous, methods for approaching this problem. n this study we have used Hartree-Fock methods in the gaussian series of programs employing the 3-21g and 6-31g* basis sets and the local density function method Dmol to obtain molecular geometries, energies and charge distributions of the epoxides and the two potential hydroxy-carbocations that could result from protonated ring opening, for a series of cPAHs. e have also performed the same calculations with AMSOL/SM2 a semi-empirical method that adds the effect of the water environment to the AM1 hamiltonian. he division of the cPAHs into classes is not altered by these more rigorous calculations. he inclusion of water in the hamiltonian has a greater effect on the results than using the ab initio methods to obtain the structure.