Brominated diphenylethers

The additional formation of PBDD from brominated diphenylether can be explained by a SET mechanism, see Scheme 3. 

Chemicals that possess a common structural feature are called congeners. Some common examples are polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), poly-brominated diphenylethers (PBDE) and chlorofluorocarbons (CFC). The common features... 

H. Thoma, G. Hauschulz, E. Knorr and O. Hutzinger, "Polybrominated Dibenzofurans (PBDF) and Dibenzodioxins (PBDD) from the Pyrolysis of Neat Brominated Diphenylethers, Biphenyls and Plastic Mixtures of these Compounds,"Chemosphere, JJi, 277(1987). 

Eriksson J, Jakobsson E, Marsh G, et al. 2001. Photo decomposition of brominated diphenylethers in methanol/water. BFR 203-206. 

Most preparation methods of PBDEs reported are patents describing the bromination of diphenylether in the presence of a catalyst [1]. This results in products containing mixtures of brominated diphenylethers (Table 3). PBDEs have not been reported to occur naturally in the environment, but the related polybrominated phenoxy phenols have been found in several marine organisms, e.g. in Dysidea herbacea, Dysidea chlorea, and Phyllospongio foliascents [3]. Vionov et al. [14] showed that the bacteria Vibrio sp. associated with the sponge Dysidea sp. is capable of producing brominated diphenylethers. 

Because of the presence of an oxygen atom, there is less similarity in the molecular structure between PBDEs and PCBs than between PBBs and PCBs [3]. The commercial PBDEs are rather stable compounds with boiling points ranging between 310 and 425 °C [3], and with low vapour pressures (Table 2 B) [1,3],The volatility of PBDEs is low and their solubility in water is very low, especially that of higher brominated diphenylethers. It was concluded that higher brominated compounds are more persistent than lower brominated compounds. PBDEs are soluble in toluene. The commercial PBDEs are lipophilic substances of which the logKow increases with increasing bromine content [3]. 

Figure 2 Demethylisodysidenin (a), Brominated diphenylether (b) from cyanobacterial symbionts of sponges.

SPMD Anthracene, Benzene, Brominated diphenylether, Cio-13-chloroalkanes,... 

Brominated diphenyls and brominated diphenylethers-for instance, octabromodiphenyl ether (melting point 200°C-290°C) and decabromodiphenyl ether (melting point 290°C-310°C)-have gained great significance. Possessing excellent heat stability, they are excellent flame retardants for those thermoplastics that have to be processed at high temperatures, such as linear polyesters and ABS. 

C in TG-FTIR measurement (792 cm ) of a brominated polystyrene sample [365]. On-the-spot TG-FTIR of PBT/octabromodiphenyl ether (MW 801 Da) detected the brominated diphenylether flame retardant at 275° C and terephthalic acid (the starting monomer of PBT) at 425°C [310]. Similar high-MW species have never been reported in TG-MS experiments the flame retardant was not observed in off-line TG-GC-FTIR-MS analysis. In an examination of an ABS/PC blend with 8% triphenylphosphate (TPP), in addition to the EGP, the SGPs for the specific wavenumber windows of TPP (900-1200 cm ), aromatic compounds (3000-3100 cm ), and carbon oxides originating from PC (2200-2300 cm ), were obtained. TPP evolving first was detected at about 150°C (detection limit 0.5 /xg/s) [310]. Anthony [366] has used FTIR spectroscopy to examine TG residues and diffuse reflectance as the means of sample preparation for the study of interactions between pyromellitate polyesters (smoke suppressants) and polyurethane foams. This was achieved by interrupting the thermal analysis at selected points on the TG curve. In... 

Salva, J. and Faulkner, D.J. (1990b) A new brominated diphenylether from a Philippine Dysidea species. J. Nat. Prod., 53, 757-760. 

---