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Dechlorination of monochlorobenzene using organic mediators ABSTRACTIn the presence of an organic mediator such as dibenzofuran, the reduction of chlorobenzene occurs indirectly and at substantially less negative potentials compared to its direct reduction at a glassy carbon cathode in acetonitrile. By using the indirect, mediator approach to reduction of chlorobenzene, constant current electrolysis at carbon plate cathodes can give complete dechlorination with high current efficiency Both divided and undivided cells were used, each having their own advantages. Besides dibenzofuran, naphthalene and biphenyl were successfully tested as organic mediators for chlorobenzene reduction. During the entire electrolysis, the mediator concentration remained practically constant so that substantially less mediator was required in comparison to the substrate, i.e., chlorobenzene. Higher concentrations of mediator can be beneficial, e.g., a dibenzofuran:chlorobenzene ratio of 2.5:5 as compared to 1:5, if the electrolysis is to be conducted at higher current density. For electrolysis of large amounts of chlorobenzene, an approach where the substrate is added periodically to a solution of the (reduced) mediator is recommended. A comparison of the results from direct vs. indirect dechlorination of chlorobenzene clearly demonstrates the substantial superiority of the latter approach.

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The mechanism and synthetic perspectives of an indirect cathodic amination of unsaturated and aromatic substrates are considered. The influence of experimental conditions on the state and reactivity of the aminating reagent in solution is studied. The key role of the electrolyte acidity and redox properties of the reagents and intermediates in the obtained isomeric composition and the yield of the amination products is demonstrated.

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