Density Functional Theory Study of Marine Polybrominated Diphenyl Ethers in Anaerobic Degradation

Polybrominated diphenyl ethers (PBDEs) are a kind of serious pollutants in the ocean. Biodegradation is considered as an economical and safe way for PBDEs removal and reductive debromination dominates the initial pathway of anaerobic degradation. On the basis of experimental study, Octa-BDE 197, Hepta-BDE 183, Hexa-BDE 153, Penta-BDE 99 and Tetra-BDE 47 were selected as the initial degradation objects, and their debromination degradation were studied using density functional theory. The structures were optimized by Gaussian 09 program. Furthermore, the molecular orbitals and charge distribution were analyzed. All C-Br bond dissociation energies at different positions including ortho, meta and para bromine atoms were calculated and the sequence of debromination was obtained. There is a close relationship between molecular structure, charge, molecular orbital and C-Br bond. All PBDEs exhibited similar debromination pathways with preferential removal of meta and para bromines.