Survey of the electrochemical behavior of chlorinated pyrazines, quinoxalines, and pyridazines at carbon and mercury cathodes

Cyclic voltammetry and controlled-potential electrolysis have been employed to examine the electrochemical behavior of some mono- and dichlorinated pyrazines, quinoxalines, and pyridazines at carbon and mercury cathodes in either acetonitrile or dimethylformamide containing a tetraalkylammonium salt. Unsubstituted pyrazine and pyridazine each exhibit a single reduction wave, whereas unsubstituted quinoxaline shows three cathodic waves. For the chlorinated compounds, an additional wave is seen for the reduction of each carbon–chlorine bond. Depending on the potential of the cathode, bulk electrolyses of dichlorinated pyrazines or quinoxalines afford either the monochlorinated or fully dechlorinated product, whereas the monochlorinated analogues undergo reduction to the dechlorinated species. Electrolyses of chlorinated pyridazines give dark colored solutions, but the products (apparently polymeric) cannot be detected or identified by means of conventional GC, GC–MS, and HPLC techniques.