Electron-induced reductive debromination of 2,3,4-tribromodiphenyl ether: a computational study.

To better understand the mechanism of the electron induced elimination of the bromide anion, we examined at the B3LYP/6-31+G(d) level electron capture by 2,3,4-tribromodiphenyl ether (BDE-21) followed by the release of the bromide anion and a radical. Both the geometry and energy of the BDE-21 neutral and its possible anionic states were studied. A significant relationship was found between the total energy and the length of the C-Br bonds by the analysis of the potential energy surface for the anionic states. Debromination preference for the bromine substituted positions was theoretically evaluated as meta-Br > ortho-Br > para-Br. The reaction profiles of the electron-induced debromination of BDE-21 demonstrated that, in general, the presence of a solvent makes the electron induced reductive debromination of BDE-21 significantly more advantageous, and the stabilization effect of the solvent on the reaction intermediates would make the electron attachment and dissociation relatively effective in comparison with the results from the gas-phase calculations.