A facile and efficient base-mediated protocol for debromination of vic-dibromides in perfluoroalkyl(aryl) compounds in aqueous medium has been demonstrated. With mild reaction conditions, the developed strategy has a good substrate scope and electron-deficient olefin products were obtained in good yields. A mechanistic explanation of the debromination is offered with three key experimental observations: (1) the reactions are accelerated by the more electron-rich nucleophiles, (2) the reactions are promoted by the more electron poor vic-dibromides in perfluoroalkyl compounds, and (3) the nucleophilic side reaction is preventable. It is evident that the electronic factors strongly dictate vic-dibromides elimination to the perfluorovinyl ethers, which are the precursors for various perfluorinated polymers. The different reaction conditions were tested in implicit solvent (water) conditions, which helped to confirm the E2-like mechanism.

<p>Polybrominated diphenyl ethers (PBDEs) are important chemical flame retardants, but also environmental pollutants. Their bromine substitution lends them a different bioaccumulation behaviour than the better studied organochlorines.</p><p>The contamination of a Swedish lake with lower brominated BDEs was assessed by a retrospective study of pike. The concentrations of tetra- to hexaBDEs increased exponentially up to the mid-1980s and then decreased slowly, possibly reflecting the voluntary reduction in production/usage of the chemicals. Methoxylated PBDEs were found to be present in similar concentrations to the PBDEs, but originated from different sources. The large size of the bromine atom was believed to result in negligible absorption of higher brominated BDEs in wildlife, thus explaining the low levels observed in fish despite high levels in e.g. sediment. However, it was shown that the fully brominated BDE, BDE209, was absorbed to a small extent via the diet. Once absorbed, it was reductively debrominated to lower brominated BDE congeners. Debromination was also observed in dairy cows exposed to higher brominated BDEs in their natural diet. Moreover, the molecular size restricted the transfer of higher brominated BDEs to milk. In contrast to PCBs and lower brominated BDEs, there was no equilibrium between adipose tissues and milk fat, and with increasing bromine substitution a progressively smaller fraction of the ingested PBDEs was transferred to the milk.</p><p>This thesis highlights differences in uptake, metabolism and excretion for PBDEs compared to the well characterized organochlorines. A knowledge that is useful for risk assessments given the ongoing use of these compounds. Furthermore, a representative of the next generation brominated flame retardants, decabromodiphenyl ethane, a replacement for the BDE209 technical product, was identified for the first time in the environment.</p>

Polybrominated diphenyl ethers (PBDEs) are important chemical flame retardants, but also environmental pollutants. Their bromine substitution lends them a different bioaccumulation behaviour than the better studied organochlorines. The contamination of a Swedish lake with lower brominated BDEs was assessed by a retrospective study of pike. The concentrations of tetra- to hexaBDEs increased exponentially up to the mid-1980s and then decreased slowly, possibly reflecting the voluntary reduction in production/usage of the chemicals. Methoxylated PBDEs were found to be present in similar concentrations to the PBDEs, but originated from different sources. The large size of the bromine atom was believed to result in negligible absorption of higher brominated BDEs in wildlife, thus explaining the low levels observed in fish despite high levels in e.g. sediment. However, it was shown that the fully brominated BDE, BDE209, was absorbed to a small extent via the diet. Once absorbed, it was reductively debrominated to lower brominated BDE congeners. Debromination was also observed in dairy cows exposed to higher brominated BDEs in their natural diet. Moreover, the molecular size restricted the transfer of higher brominated BDEs to milk. In contrast to PCBs and lower brominated BDEs, there was no equilibrium between adipose tissues and milk fat, and with increasing bromine substitution a progressively smaller fraction of the ingested PBDEs was transferred to the milk. This thesis highlights differences in uptake, metabolism and excretion for PBDEs compared to the well characterized organochlorines. A knowledge that is useful for risk assessments given the ongoing use of these compounds. Furthermore, a representative of the next generation brominated flame retardants, decabromodiphenyl ethane, a replacement for the BDE209 technical product, was identified for the first time in the environment.