COPPER-PROMOTED REACTIONS OF POLYBROMINATED DIBENZO-PARA-DIOXINS (PBRDD)

Heterogeneously catalyzed reactions were formerly shown to be involved in the formation and decomposition of polychlorinated dibenzo-para-dioxins (PCDDs) and related compounds during various combustion processes. In this paper we present investigations of the reactions of the corresponding brominated compounds - particularly 1,2,3,4-tetrabromodibenzodioxin (T4BrDD) - catalyzed by copper powder at temperatures between 100°C und 210°C. To some extent the PBrDDs were debrominated/hydrogenated to PBrDDs of a lower degree of bromination. It is also likely that an Ullmann type coupling reaction of PBrDD molecules forming a carbon-carbon bond occurs. Dibenzodioxin-dimers could be identified in the reaction products of monobromodibenzodioxin (M1BrDD)/copper-mixtures. The dependence of the rate, course and stereochemistry of the reactions on temperature, copper/PBrDD ratio and the presence of water is discussed. © 1990.