| Résumé | The use of a range of mediators for the partial or complete dechlorination of a series of polychlorinated benzenes has been investigated. The dechlorinations were carried out in acetonitrile, and the products were analyzed by gas chromatography-mass spectroscopy (GC-MS). The partial dechlorination using organic mediators was successful and good control of the reaction (i.e., monodechlorination) and good efficiency could be achieved. Some mediators showed poor current efficiencies due to the lower stability of their anion radical in the presence of protons. The monodechlorination of trichlorobenzene with four different mediators showed that the product distribution in terms of initial chlorine removed was little affected by the mediator used. This product distribution has also been investigated for the whole series of polychlorobenzenes. Polydechlorination using a single mediator was tried using biphenyl, anthracene, and dibenzofuran. After passing enough charge to completely dechlorinate trichlorobenzene, few chlorinated benzenes remained in solution and less than the expected amount of benzene was detected. The was explained by nonvolatile products undetected by GC-MS. It is suggested that when higher overpotential mediators are used, the reaction shifts to produce higher molecular weight products by radical-radical coupling reactions. Biphenyl might be a convenient mediator for the dechlorination of polychlorobenzene or even polychlorobiphenyl. |
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