Formation of bromophenoxy radicals from complete series reactions of bromophenols with H and OH radicals.

The bromophenoxy radicals (BPRs) are key intermediate species involved in the formation of polybrominated dibenzo-p-dioxin/dibenzofurans (PBDD/Fs). In this work, the formation of BPRs from the complete series reactions of 19 bromophenol (BP) congeners with H and OH radicals were investigated theoretically by using the density functional theory (DFT) method and the direct dynamics method. The geometries and frequencies of the reactants, transition states, and products were calculated at the MPWB1K/6-31+G(d,p) level, and the energetic parameters were further refined by the MPWB1K/6-311+G(3df,2p) method. The rate constants were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) contribution over a wide temperature range of 600-1200K. The present study indicates that the reactivity of the O-H bonds in BPs as well as the formation potential of BPRs from BPs is strongly related to the bromine substitution pattern. The obtained results can be used for future estimates of PBDD/F emissions quantity based on the well estimated PCDD/F inventory.