title: Structure characterization and thermal stabilities of the isomers of the brominated flame retardant 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane.
abstract: 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.
authors.affiliation: Wellington Laboratories, Research Division, Guelph, ON, Canada N1G 3M5. gilles@well-labs.com
authors.forename: Gilles
authors.initials: G
authors.lastname: Arsenault
authors.forename: Alan
authors.initials: A
authors.lastname: Lough
authors.forename: Chris
authors.initials: C
authors.lastname: Marvin
authors.forename: Alan
authors.initials: A
authors.lastname: McAlees
authors.forename: Robert
authors.initials: R
authors.lastname: McCrindle
authors.forename: Gordia
authors.initials: G
authors.lastname: MacInnis
authors.forename: Kerri
authors.initials: K
authors.lastname: Pleskach
authors.forename: Dave
authors.initials: D
authors.lastname: Potter
authors.forename: Nicole
authors.initials: N
authors.lastname: Riddell
authors.forename: Ed
authors.initials: E
authors.lastname: Sverko
authors.forename: Sheryl
authors.initials: S
authors.lastname: Tittlemier
authors.forename: Gregg
authors.initials: G
authors.lastname: Tomy
mesh_terms: 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
chemical_list: D003510:Cyclohexanes; D005411:Flame Retardants; C517232:1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane; D001966:Bromine