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Polybrominated diphenyl ethers and Tetrabromobisphenol A: Chemical synthesis, X-ray crystallography and Photochemical degradation
Stockholm University, Faculty of Science, Department of Environmental Chemistry.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the 1960s’ several manmade chemicals were detected in the environment, far from their sources. The most well known, and most likely those with the largest impact on the society, were DDT and its related compounds, and PCBs. These anthropogenic compounds were characterised as persistent organic pollutants (POPs). Following these POPs, several other chemicals have found their way to the environment. Over the last two decades, brominated flame retardants (BFRs) have become a matter of concern. Among all BFRs being commercially produced, tetrabromobisphenol A (TBBPA) and polybrominated diphenyl ethers (PBDEs) are the ones with the largest annual production. TBBPA is a very well defined compound while PBDEs consist of a large number of isomers and homologues (congeners). TBBPA does not seem to accumulate in biota as the PBDEs do, but is still of concern since it is found in e.g. sediments. The PBDEs can reach accumulation levels up in the ppm range. Still there is a lack of basic data for both TBBPA and PBDEs. Hence the present thesis is aimed to fill some of the data gaps by pursuing work on 1) photochemical degradation of TBBPA, some related compounds, and PBDEs; 2) synthesis of PBDE congeners and of TBBPA degradation products and 3) structural identifications of a selected set of BFRs by X-ray crystallography.

An apparatus was designed for carrying out photochemical degradation test of chemicals in general but in particular for BFRs. Quantum yield, rate of degradation and to some extent, identification of degradation products were performed on TBBPA, the corresponding chlorinated compound and a number of TBBPA degradation products and on 15 single PBDE congeners. In order to make this work possible all three nonaBDE isomers were synthesised via a reductive pathway applying sodium borohydride as a reducing agent. The three nona-BDEs were all characterised by X-ray crystallography.

The results of the photochemical degradation of TBBPA in water show a rapidly degradable compound also at pH’s that are environmentally relevant. Hence it is likely that TBBPA is not transported long distances, when exposed to sunlight, without undergoing photochemical degradation. It is notable that the TBBPA is degraded through cleavage between the two phenol rings. When the method was applied to study quantum yields and rate constants for the reaction of PBDE congeners it is evident that the decabromodiphenyl ether (BDE-209) is rapidly transformed. The reaction rate differ drastically from PBDEs with four or five bromine substituents that have very long half-lives when subjected to UV-light under the same conditions as for BDE-209. Lower brominated diphenyl ethers and polybrominated dibenzofurans were identified as PBDE degradation products. The synthesis of PBDEs and of TBBPA degradation products expanded the study as did the X-ray structure identifications.

Place, publisher, year, edition, pages
Stockholm: Institutionen för miljökemi , 2004. , 96 p.
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-167ISBN: 91-7265-878-9 (print)OAI: oai:DiVA.org:su-167DiVA: diva2:190400
Public defence
2004-06-04, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-05-13 Created: 2004-05-13Bibliographically approved
List of papers
1. Photochemical transformations of tetrabromobisphenol A and related phenols in water
Open this publication in new window or tab >>Photochemical transformations of tetrabromobisphenol A and related phenols in water
Show others...
2004 (English)In: Chemosphere, ISSN 0045-6535, Vol. 54, no 1, 117-126 p.Article in journal (Refereed) Published
Abstract [en]

romobisphenolA (TBBPA), tribromobisphenol A (TriBBPA), tetrachlorobisphenol A (TCBPA), 2,4-dichlorophenolat various pHs as well as 2-chlorophenol, 2-bromophenol, 3,4-dichlorophenol and bisphenol A at pH 11. The absorbancespectra of the compounds and the emission spectra of the light-source were determined and used to calculatedisappearance quantum yields of the photochemical reactions that were taking place. No major differences between thedisappearance quantum yields of TBBPA and TCBPA were observed at pH 10, while the disappearance quantum yieldof TriBBPA was approximately two times higher. The rate of decomposition of TBBPA was six times higher at pH 8than at pH 6. Identification of the degradation products of TBBPA and TriBBPA, by GC–MS analysis and bycomparison to synthesised reference compounds, indicated that TBBPA and TriBBPA decompose via differentmechanisms. Three isopropylphenol derivatives; 4-isopropyl-2,6-dibromophenol, 4-isopropylene-2,6-dibromophenoland 4-(2-hydroxyisopropyl)-2,6-dibromophenol, were identified as major degradation products of TBBPA while themajor degradation product of TriBBPA was tentatively identified as 2-(2,4-cyclopentadienyl)-2-(3,5-dibromo-4-hydroxyphenyl)propane.

Place, publisher, year, edition, pages
Elsevier, 2004
Keyword
Tetrabromobisphenol A; Brominated flame retardants; Reactivity; Photodegradation
National Category
Environmental Sciences
Identifiers
urn:nbn:se:su:diva-23144 (URN)10.1016/S0045-6535(03)00704-5 (DOI)
Note
Part of urn:nbn:se:su:diva-167Available from: 2004-05-13 Created: 2004-05-13 Last updated: 2009-12-21Bibliographically approved
2. Photochemical decomposition of fifteen polybrominated diphenyl ether congeners in methanol/water
Open this publication in new window or tab >>Photochemical decomposition of fifteen polybrominated diphenyl ether congeners in methanol/water
2004 (English)In: Environmental Science & Technology, ISSN 1520-5851, Vol. 38, no 11, 3119-3125 p.Article in journal (Refereed) Published
Abstract [en]

Among all brominated flame retardants in use, the polybrominated diphenyl ethers (PBDEs) have been identified as being of particular environmental concern due to their global distribution and bioaccumulating properties, as observed in humans and wildlife worldwide. Still there is a need for more data on the basic characteristics of PBDEs to better understand and describe their environmental fate. Hence, the aim of this study was to investigate the photochemical degradation of PBDEs with different degrees of bromination. The photochemical degradation of 15 individual PBDEs substituted with 4−10 bromine atoms was studied in methanol/water (8:2) by UV light in the sunlight region. Nine of these were also studied in pure methanol, and four of the nine PBDEs were studied in tetrahydrofuran. The photochemical reaction rate decreased with decreasing number of bromine substituents in the molecule but also in some cases influenced by the PBDE substitution pattern. The reaction rate was dependent on the solvent in such a way that the reaction rate in a methanol/water solution was consistently around 1.7 times lower than in pure methanol and 2−3 times lower than in THF. The UV degradation half-life of decaBDE (T1/2 = 0.5 h) was more than 500 times shorter than the environmentally abundant congener 2,2‘,4,4‘-tetraBDE (T1/2 = 12 d) in methanol/water. The quantum yields in the methanol/water solution ranged from 0.1 to 0.3. The photochemical reaction of decaBDE is a consecutive debromination from ten- down to six-bromine-substituted PBDEs. Products with less than six bromines were tentatively identified as brominated dibenzofurans and traces of what was indicated as methoxylated brominated dibenzofurans.

Place, publisher, year, edition, pages
American Chemical Society, 2004
National Category
Environmental Sciences
Research subject
Environmental Chemistry
Identifiers
urn:nbn:se:su:diva-23145 (URN)10.1021/es049830t (DOI)
Note
Part of urn:nbn:se:su:diva-167Available from: 2004-05-13 Created: 2004-05-13 Last updated: 2009-12-22Bibliographically approved
3. 2,2’,6,6’-Tetrachloro-4,4’-propane-2,2-diyldiphenol, 2,2’,6-tribromo-4,4’-propane-2,2-diyldi phenol and 2,2’,6,6’-tetrabromo-4,4’-propane-2,2-diyldiphenol
Open this publication in new window or tab >>2,2’,6,6’-Tetrachloro-4,4’-propane-2,2-diyldiphenol, 2,2’,6-tribromo-4,4’-propane-2,2-diyldi phenol and 2,2’,6,6’-tetrabromo-4,4’-propane-2,2-diyldiphenol
2001 (English)In: Acta crystallographica Section C, ISSN 0108-2701, Vol. 57, no 11, 1308-1312 p.Article in journal (Refereed) Published
Abstract [en]

Three flame retardants with very similar molecular structures showing three different packing patterns have been studied. The crystal structure of 2,2',6,6'-tetrachloro-4,4'-propane-2,2-diyldiphenol, C15H12Cl4O2, can be described as a packing of sheets. The packing shows a very short intermolecular ClCl contact distance of 3.094  (2)  Å between pairs of molecules inside each sheet. The crystal structure of 2,2',6-tribromo-4,4'-propane-2,2-diyldiphenol, C15H13Br3O2, can be described as a packing of doubly stranded helical square tubes. These square helices are interconnected through BrBr contacts between different helices. Finally, a previously known structure, 2,2',6,6'-tetrabromo-4,4'-propane-2,2-diyldiphenol [Simonov, Cheban, Rotaru & Bels'skii (1986). Kristallografiya, 31, 397-399], C15H12Br4O2, which is the most commonly used flame retardant and which has twofold rotational symmetry, has been refined in the correct absolute configuration. The structure shows large differences from the chloro analogue with regard to packing, van der Waals distances and hydrogen-bond distances.

Place, publisher, year, edition, pages
Wiley, 2001
National Category
Chemical Sciences
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-23146 (URN)10.1107/S0108270101012112 (DOI)
Note
Part of urn:nbn:se:su:diva-167Available from: 2004-05-13 Created: 2004-05-13 Last updated: 2009-12-22Bibliographically approved
4. Decabromodiphenyl ether
Open this publication in new window or tab >>Decabromodiphenyl ether
1999 (English)In: Acta crystallographica Section C, ISSN 0108-2701, Vol. 55, no 12, 2169-2171 p.Article in journal (Refereed) Published
Abstract [en]

Bis(pentabromophenyl) ether, C12Br100, shows strangedifferences in the endocyclic angles between the twodifferent rings, although they are both substituted inthe same manner. Several short van der Waals contact distances give clues to the anomalous endocyclic anglesand some hints to the formation of decompositionproducts. We suggest that the intermolecular Br...Brcontacts contribute to the distortions of the ring systems.Usually distortions of this kind would be explained fromhighly anisotropic TLS behaviour, but the data from thetitle compound do not show any conclusive TLS effects.

Place, publisher, year, edition, pages
Wiley, 1999
National Category
Other Basic Medicine
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-23147 (URN)10.1107/S0108270199008884 (DOI)
Note
Part of urn:nbn:se:su:diva-167Available from: 2004-05-13 Created: 2004-05-13 Last updated: 2009-12-22Bibliographically approved
5. 3,4,5,6-Tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O, 2,4,5,6-tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O and 2,3,5,6-tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O
Open this publication in new window or tab >>3,4,5,6-Tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O, 2,4,5,6-tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O and 2,3,5,6-tetrabromo phenyl-2,3,4,5,6-pentabromo phenyl ether, C12HBr9O
2004 (English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Identifiers
urn:nbn:se:su:diva-23148 (URN)
Note
Part of urn:nbn:se:su:diva-167Available from: 2004-05-13 Created: 2004-05-13 Last updated: 2010-01-29Bibliographically approved

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