On the de novo synthesis of polychlorinated dibenzo-p-dioxins and dibenzofurans.

Some possible intermediates or by-products in the synthesis of polychlorodibenzo-p-dioxins and dibenzofurans in municipal waste incinerators are presented. In stack gas samples from two different incinerators, the following compounds were tentatively identified: polychloromonobenzofurans, polychloromonobenzodioxins, monobromo-polychlorobenzenes and polychlorothiophenes. The occurrence of complete series of homologues and isomers with an increasing degree of chlorination suggests an analogous formation mechanism with common precursors. The presence of these compounds in the vapour phase, the non-regiospecific character of these reactions and the high reaction temperature and speed confirm a radical mechanism of formation.