Polychlorobiphenyls formed from Chlorobenzenes and Dibenzoyl peroxides

When dibenzoyl peroxide (DBP) or bis(2,4‐dichlorobenzoyl) peroxide (2,4‐DCBP) decomposes in the presence of a chlorobenzene (CB), a complex polychlorobiphenyl (PCB) mixture is formed. Aryl radicals are formed from DBP or 2,4‐DCBP and they are involved in several reaction pathways: in addition to CB followed by (a) H displacement or by (b) Cl displacement; in (c) H abstraction or in (d) Cl abstraction from CB and addition of the formed CB radical to another CB molecule followed by H displacement or by Cl displacement; in (e) H addition to CB or a PCB followed by Cl displacement. Reaction pathway (a) is the major one. It favours the formation of PCB isomers substituted 2,6‐ > 2‐ > non‐ortho in the case of DBP, and 2,2’, 6‐ > 2‐> 2,2'‐ in the case of 2,4‐DCBP. Reaction pathway (b) is minor in the case of lower substituted CBs and may be important at higher substituted CBs, especially when they have more than two adjacent chlorines. Reaction pathways (c) and (d) are minor ones, too, and of similar probability...

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