Structure characterization and thermal stabilities of the isomers of the brominated flame retardant 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane.
1,2-Dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) is used primarily as an additive flame retardant. 1H NMR spectroscopy and an X-ray structure determination have revealed that a technical mixture consists largely of two (of the four possible) diastereomers, rac-(1R,2R)-1,2-dibromo-(4S)-4-((1S)-1,2-dibromoethyl)cyclohexane (alpha-TBECH) and rac-(1R,2R)-1,2-dibromo-(4S)-4-((1R)-1,2-dibromoethyl)cyclohexane (beta-TBECH), in a mole ratio of approximately 1:1. The two other possible isomers, gamma- and delta-TBECH, were not detected in a technical mixture. The TBECH isomers are thermally sensitive and can easily interconvert at temperatures of 125 degrees C. A thermal equilibrium mixture of alpha-, beta-, gamma- and delta-TBECH consists of approximately 33%, 33%, 17% and 17% of these isomers, respectively. Separation of all four TBECH diastereomers, with minimal thermal interconversion of the isomers, was achieved by careful selection of GC-capillary column length and injector temperature. Although technical TBECH does not contain the gamma- and delta-isomers, they may still be relevant environmental contaminants since manufacturing processes utilize thermal processes which may induce their formation.
Arsenault
Gilles
G
Wellington Laboratories, Research Division, Guelph, ON, Canada N1G 3M5. gilles@well-labs.com
Lough
Alan
A
Marvin
Chris
C
McAlees
Alan
A
McCrindle
Robert
R
MacInnis
Gordia
G
Pleskach
Kerri
K
Potter
Dave
D
Riddell
Nicole
N
Sverko
Ed
E
Tittlemier
Sheryl
S
Tomy
Gregg
G
D001966:Bromine / Q000737:chemistry; D003510:Cyclohexanes / Q000737:chemistry*; D005411:Flame Retardants / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry; D054879:Halogenation; D006358:Hot Temperature; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure
D003510:Cyclohexanes; D005411:Flame Retardants; C517232:1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane; D001966:Bromine