Atmospheric chemical reaction mechanism and kinetics of 1,2-bis(2,4,6-tribromophenoxy)ethane initiated by OH radical: a computational study

Abstract

The unexpected diverse effect of alternatives for banned chemicals has stimulated scientific and public concern on their environmental risk. As an alternative of polybrominated diphenyl ethers (PBDEs), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE) is currently one of the most commonly applied novel brominated flame retardants with wide market prospects. Due to its frequent and high detection in the atmosphere, revealing the atmospheric fate of BTBPE is of great significance. Here, the mechanism and kinetics of the ·OH-initiated atmospheric reaction of BTBPE have been investigated by combined quantum chemical calculations and kinetics modeling. The results indicate that ·OH addition and hydrogen abstraction pathways in the initiated reactions, are competitive with a rate constant ratio of 3 : 1, and the intermediates formed would react with O₂/NO to finally form peroxy radicals and OH-BTBPE which tends to be more toxic. The calculated overall reaction rate constant is 1.0 × 10⁻¹² cm³ per molecule per s, translating into 11.8 days atmospheric lifetime of BTBPE. This clarifies that BTBPE as a substitute for PBDEs still has atmospheric persistence.