MECHANISTIC STUDIES ON THE ELECTROCHEMICAL REDUCTIVE COUPLING OF SOMEPOLYHALOGENONITROBENZENES - A NEW EXAMPLE OF A RADICAL-ANION DIMERIZATION

Coupling processes with loss of one halogen atom per ring are observed when heavily substituted polyhalogenonitrobenzenes (polyfluoro- and p olychloro-) are electrochemically reduced in DMF. Product analyses and cyclic voltametry mechanistic studies suggest that in the particular case of pentafluoronitrobenzene, direct dimerization of the radical an ions occurs prior to C-F bond fragmentation. On the contrary, reductio n of the nitro group is the only observed process when less substitute d polyhalogenonitrobenzenes are used in the same conditions. Nitro gro up reduction is also the main process for all the studied polyhalogeno nitrobenzenes when the reactions are carried out in protic solvents.