Photolytic debromination and degradation of decabromodiphenyl ether, an exploratory kinetic study in toluene

The photolysis of decabromodiphenyl ether, dissolved in toluene, was studied using a filtered Xe lamp as solar simulator. A loss of decabromodiphenyl ether, leading to unknown products, and sequential debromination via the nona-, octa-, heptabromodiphenyl ethers was observed. The photolytic rate constant of decabromodiphenyl ether, kphot = 3·10-4s-1, indicated a high quantum yield > 0.1, of which more than 50% leads to debromination. The debromination rate constants decreased with the debromination steps, and the decrease can be explained by the decreasing overlap of the UV absorption spectra of the compounds with the spectrum of the lamp, where the decrease can be expected to be similar for sunlight. The UV absorption spectra of diphenylether, 4-bromodiphenyl ether, 4,4-dibromodiphenyl ether and decabromodiphenyl ether, dissolved in toluene, are presented for the first time. The spectra in the wavelength range from 290 to 360 nm imply a strong diurnal, seasonal and latitudinal dependence of environmental photolysis rates.