Degradation mechanisms and dehalogenation of polychlorinated aromatics were investigated using the alkali polyethyleneglycolate (APEG)-PLUS™ technique. It was found that a bundle of very different chlorophenols, alkoxyphenols and benzenes were furnished by several successive and competing reactions, mainly involving S_NAr and aryne mechanisms. It was observed that 100% of the organic chlorine bound to the parent polychlorinated aromatic molecule were not removed. The results show that hazardous phenols can be generated to a greater extent by the reactions of poluchlorinated benzenes and PCBs with alcoholate/dimethylsulfoxide (DMSO).