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 py razines, quinoxalines, and pyridazines at carbon and mercury cathodes in ei ther acetonitrile or dimethylformamide containing a tetraalkylammonium salt . Unsubstituted pyrazine and pyridazine each exhibit a single reduction wav e, whereas unsubstituted quinoxaline shows three cathodic waves, For the ch lorinated compounds, an additional wave is seen for the reduction of each c arbon-chlorine bond. Depending on the potential of the cathode, bulk electr olyses of dichlorinated pyrazines or quinoxalines afford either the monochl orinated or fully dechlorinated product, whereas the monochlorinated analog ues undergo reduction to the dechlorinated species. Electrolyses of chlorin ated 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. (C) 2001 Elsevier Science B.V. All rights reserve d.