Structural characterization and thermal stabilities of the isomers of the brominated flame retardant 1,2,5,6-tetrabromocyclooctane (TBCO)

• Published in: Chemosphere (Oxford) Vol. 74; no. 11; pp. 1538 - 1543
• Main Authors: Riddell, Nicole, Arsenault, Gilles, Klein, Jeff, Lough, Alan, Marvin, Chris H., McAlees, Alan, McCrindle, Robert, MacInnis, Gordia, Sverko, Ed, Tittlemier, Sheryl, Tomy, Gregg T.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2009; Elsevier
• Subjects: Applied sciences; BFR; Chromatography, High Pressure Liquid; Conformation; Crystal structure; Crystallography, X-Ray; Cyclooctanes - analysis; Cyclooctanes - chemistry; Drug Stability; Exact sciences and technology; Flame Retardants - analysis; Gas Chromatography-Mass Spectrometry; GC/MS; Global environmental pollution; Hot Temperature; Hydrocarbons, Brominated - analysis; Hydrocarbons, Brominated - chemistry; Isomerism; LC/MS; Magnetic Resonance Spectroscopy; NMR spectroscopy; Pollution; LC/MS; NMR spectroscopy; GC/MS; Crystal structure; Conformation; BFR; Bromocarbon; Flame retardant; Organic bromine compounds; Liquid chromatography; NMR spectrometry; Stereochemistry; Thermal stability; Gas chromatography; Pollution; Saturated cyclic compound; Environment; Mass spectrometry; Diastereomer; Organic compounds; Crystalline structure
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2008.11.026

1,2,5,6-Tetrabromocyclooctane (TBCO) is a commercial brominated flame retardant that is employed mainly as an additive in textiles, paints and plastics. Very little is known about its presence or behavior in the environment or its analysis. TBCO can exist as two diastereomers, the stereochemistries of which have not been previously reported. We have named the first eluting isomer, under HPLC conditions, as alpha-TBCO (α-TBCO) and the later eluting isomer as beta-TBCO (β-TBCO) when using an Acquity UPLC BEH C 18 column with methanol/acetonitrile/water as the mobile phase. The structural elucidation of these two isomers was accomplished by 1H NMR spectroscopy, GC/MS, LC/MS and X-ray structure determinations. α-TBCO is (1 R,2 R,5 S,6 S)-1,2,5,6-tetrabromocyclooctane and β-TBCO is rac-(1 R,2 R,5 R,6 R)-1,2,5,6-tetrabromocyclooctane. As with some other brominated cycloaliphatic compounds, TBCO is thermally labile and the isomers easily interconvert. A thermal equilibrium mixture of α- and β-TBCO consists of approximately 15% and 85% of these isomers, respectively. Separation of the two diastereomers, with minimal thermal interconversion between them, is achievable by careful selection of GC-capillary column length and injector temperature. LC/MS analyses of TBCO also presents an analytical challenge due to poor resolution of the isomers on chromatographic stationary phases, and weak intensity of molecular ions (or major fragment ions) when using LC-ESI/MS. Only bromide ions were seen in the mass spectra. APCI and APPI also failed to produce the molecular ion with sufficient intensity for identification.