Structural characterization and thermal stabilities of the isomers of the brominated flame retardant 1,2,5,6-tetrabromocyclooctane (TBCO).
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 (alpha-TBCO) and the later eluting isomer as beta-TBCO (beta-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. alpha-TBCO is (1R,2R,5S,6S)-1,2,5,6-tetrabromocyclooctane and beta-TBCO is rac-(1R,2R,5R,6R)-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 alpha- and beta-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.
Riddell
Nicole
N
Wellington Laboratories Inc., Research Division, 345 Southgate Drive, Guelph, Ontario N1G3M5, Canada.
Arsenault
Gilles
G
Klein
Jeff
J
Lough
Alan
A
Marvin
Chris H
CH
McAlees
Alan
A
McCrindle
Robert
R
Macinnis
Gordia
G
Sverko
Ed
E
Tittlemier
Sheryl
S
Tomy
Gregg T
GT
D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D034242:Cyclooctanes / Q000032:analysis / Q000737:chemistry*; D004355:Drug Stability; D005411:Flame Retardants / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D006842:Hydrocarbons, Brominated / Q000032:analysis / Q000737:chemistry*; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy
C540596:1,2,5,6-tetrabromocyclooctane; D034242:Cyclooctanes; D005411:Flame Retardants; D006842:Hydrocarbons, Brominated