Chemical reactivity, biotransformation, and toxicity of polychlorinated aliphatic compounds.

Abstract

The metabolic transformation of chlorinated aliphatic hydrocarbons to reactive intermediates is predominantly determined by the number of chlorine substitutions and the type of C-C bonds. Due to their electron-attracting effect, chlorine residues exert a destabilization in alkanes, resulting in metabolic conversions to either alkenes (dechlorination or dehydrochlorination) or free radicals. Chlorinated alkenes are enzymatically oxidized to epoxides which may be hydrolized (enzymatically or nonenzymatically), react with cellular nucleophiles, or rearrange to either chlorinated aldehydes or acyl chlorides. In the series of chlorinated ethylenes (tetra-, tri-, 1,2-cis- and trans-di-, 1,1-di-, and monochloroethylene) the metabolites thus far identified are identical to or biological conjugates of the expected thermal rearrangement products of the epoxides, with one important exception: trichloroethylene. The thermal rearrangement of this epoxide leads to dichloroacetylchloride; in vivo, however, only chloral ...