Effect of Various Factors on Dehalogenation of Chlorinated Phenols and Anilines during Oxidative Coupling

摘要

According to previous research, dehalogenation of chlorinated phenols in the presence of horseradish peroxidase or Trametes versicolor laccase is due to the free-radical mechanism of an oxidative coupling reaction. This study demonstrated that short reaction time, limited amount of catalyst, or unfavorable pH conditions may result in an insufficient generation of free radicals and a reduction in dehalogenation of chlorinated phenols. The free-radical mechanism of chloride release was also found to be valid for peroxidase-mediated polymerization of chlorinated anilines. In the case of a tyrosinase-mediated polymerization of chlorophenols, chloride ions were apparently removed from the formed o-quinones during nucleophilic attack by phenoxide ions. The results obtained strongly support the hypothesis that dehalogenation is strictly connected to oxidative coupling and cannot be enhanced independently by adjustment of the reaction conditions.