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CALCULATED MOLECULAR STRUCTURES AND POTENTIAL ENERGY FUNCTIONS OF PAHS WITH METHYL CROWDING IN THE BAY REGION AND THEIR METABOLITES: COMPARISON TO EXPERIMENTAL STRUCTURES
Citation:
Little, S., K. W. Brown, AND J. R. Rabinowitz. CALCULATED MOLECULAR STRUCTURES AND POTENTIAL ENERGY FUNCTIONS OF PAHS WITH METHYL CROWDING IN THE BAY REGION AND THEIR METABOLITES: COMPARISON TO EXPERIMENTAL STRUCTURES. Presented at NCSU Dept. of Environmental and Molecular Toxicology, Building dedication and student research symposium, Raleigh, NC, 10/22/2001.
Description:
Abstract Title: Calculated molecular structures and potential energy functions of P AHs with methyl crowding in the bay region and their metabolites: Comparison to experimental structures.
Abstract:
PAHs with methyl group substitution near a bay region represent a class of chemicals ssociated with increased risk of carcinogenesis. Methylation of the carbon atom vicinal to the benzylic bay region results in a pseudo fjord region. Molecules of this type have steric crowding similar to PAHs with a fused ring crowding the bay region, but generally have less deviation from planarity. This difference results from the rotational freedom of the methyl group and the deformation energy differences between the aromatic Csp2- Csp2 bond and the methyl Csp3-Csp2 bond. The deviation from planarity for some of these molecules based on crystallographic measurements is small. Those measurements show 5-methylchrysene to be planar. In this study the potential energy surfaces for the distortion of the bay region and vicinal methyl group of 5-methylchrysene, some of its metabolites and other similar molecules are computed using quantum mechanical methods. Stable structures for these molecules are also identified. These calculations show 5-methylchrysene as a nonplanar molecule needing only 0.5 kcal/mole to become planar .These potential energy functions are compared to similar alculations for PAHs with a fjord region. This abstract does not necessarily reflect EP A policy. All research was conducted at the National Health and Environmental Effects Research laboratory of EPA