Chlorinated Hydroxy biphenyls

When biphenyl is either chlorinated or brominated in the presence of iron(III) or antimony(V)chloride, 2- and 4-halogenated biphenyls are formed. Their hydrolysis, however, requires, strong conditions such as heating in fused potassium/sodium hydroxide with copper at 250-300°. This can cause some isomerization to 3-hydroxy-biphenyl via an aryne mechanism 67). 

For polychlorinated biphenyls (PCBs), rate constants were highly dependent on the number of chlorine atoms, and calculated atmospheric lifetimes varied from 2 d for 3-chlorobiphenyl to 34 d for 236-25 pentachlorobiphenyl (Anderson and Hites 1996). It was estimated that loss by hydroxy-lation in the atmosphere was a primary process for the removal of PCBs from the environment. It was later shown that the products were chlorinated benzoic acids produced by initial reaction with a hydroxyl radical at the 1-position followed by transannular dioxygenation at the 2- and 5-positions followed by ring fission (Brubaker and Hites 1998). Reactions of hydroxyl radicals with polychlorinated dibenzo[l,4]dioxins and dibenzofurans also play an important role for their removal from the atmosphere (Brubaker and Hites 1997). The gas phase and the particulate phase are in equilibrium, and the results show that gas-phase reactions with hydroxyl radicals are important for the... 

The formation of 3-hydroxy-2,2 5,5 tetraCB as a metabolic product of 2,2 5,5 tetraCB suggested that a nonarene oxide direct hydroxylation mechanism is an alternative metabolic route for some chlorinated biphenyl congeners (Billings and McMahon 1978 Preston et al. 1983). Sipes and Schnellmann (1987) review and confirm additional routes for PCB oxidative metabolism. 

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