Formation of octachloroacenaphthylene in the pyrolysis of decachlorobiphenyl

The pyrolytic degradation of decachlorobiphenyl (PCB 209) in the temperature range of 700 – 1000°C and at a pyrolysis time of 10 seconds generated one main chloroaromatic product. This Compound has been identified by HPLC-UV, GC-MS, GC-FTIR and 13C-NMR as octachloroacenaphthylene (OCAN). The mechanism of the nearly quantitative formation of octachloroacenaphthylene (OCAN) occurs via a nonachlorobenzobarrylene radical (ZIR) as an intermediate followed by a rearrangement and further dechlorination to for OCAN. Calculations with the program THERM based on the Benson-group-theory indicated that this mechanism is not possible for lower nonchlorinated biphenyls.