Formation of dibenzodioxins and other condensation products from chlorinated phenols and derivatives.

Chlorodioxins can be formed in a two-step condensation reaction from ortho-substituted chlorophenoxy radicals or anions (1-3). The first route is of significance only where strongly oxidizing conditions exist such as a reaction of chlorine with pentachlorophenol at elevated temperature. For the second route we have investigated the condensation of alkali metal salts of chlorinated phenols which occurs spontaneously when these metal salts are heated to temperatures above 300°C. Since this reaction is strongly exothermic, it proceeds to completion in a very narrow temperature range once initiated. For bimolecular reactions involving ortho chlorines of both phenate molecules, dioxins would be formed according to the scheme shown in eq. (1) as one of the possible reaction pathways. If these phenates contain halogen substituents in meta or para positions, these also are involved in the condensation reactions and the product distribution depends on a variety of factors such as (1) the total number of halogen substituents which determines the ease of removal of halogen; (2) the arrangement of the molecules within a crystal if this reaction takes place in the solid state, which in turn is influenced by the metal cation involved; (3)