ELECTROCHEMICAL DEBROMINATION OF 1-ARYL-1,2-DIBROMO-2-NITROPROPANES IN DIMETHYL-SULFOXIDE

Electrochemical debromination reactions of erythro-dl-1-aryl-1,2-dibro mo-2-nitropropanes 1a-d at a platinum electrode have been investigated by cyclic voltammetry in 0.10 M LiClO4/DMSO. The reactions produced ( E)-1-aryl-2-nitropropenes 2a-d in high yields. The cyclic voltammogram s were irreversible and the reduction current decreased as the number of cycles increased. The peak potential for the reductions waves are i n the range of -0.51 to -0.56 V (vs Ag/Ag+) and show no clear trend wi th different aryl substituent. The current density increased as the co ncentration of the substrate increased. The slopes of the plots of log (I/A) vs log[C] are close to unity, indicating unimolecular processes. For all reactions, the Tafel slopes are in the range of 115-125 mV. T he logarithm of the ratio i(X)/i(H) at -0.16 V did not correlate with the Hammett substituent constants. From these results, the mechanism o f these reactions is assessed.