Rapid synthesis of some lower brominated C-13-labelled dibenzo-p-dioxins and dibenzofurans and mixed brominated/chlorinated dibenzo-p-dioxins

A rapid synthesis of C-13(12)-labelled mono- and dibromodibenzo-p-dioxin and mono-, di- and tribromodibenzofuran isomers is described. Commercially available C-13(12)-2,3,7-tribromodibenzo-p-dioxin and 2,3,7,8-tetrabromodibenzofuran dissolved in n-alkanes were irradiated for several minutes using UV light. This resulted in one or two predominant isomers for each of the above mentioned homologue groups. For theoretical reasons all congeners should be substituted only at lateral positions. When C-13(12)-2,3,7,8-tetrabromodibenzo-p-dioxin was irradiated in carbon tetrachloride, Br/Cl exchange took place to yield all three 2,3,7,8-substituted mixed halogenated dibenzo-p-dioxins (Br3ClDD, Br2Cl2DD, BrCl3DD) as well as 2,3,7,8-Cl4DD. A clean-up of the resulting mixtures was not necessary. The yield was better than 50% in each case. The procedure is simple and the handling of toxic substances is reduced to a minimum. The prepared substances can be used as internal standards for the analysis of brominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans.