NUCLEOPHILIC DISPLACEMENT OF THE NITRO-GROUP OF DINITROBENZENES BY ELECTROGENERATED POLYSULFIDE IONS IN DIMETHYLACETAMIDE

Nucleophilic substitutions of ortho or para dinitroaromatics by electr ogenerated polysulfide ions S3.- (reversible S-6(2-)) have been studie d by use of spectroelectrochemistry in dimethylacetamide on 1,4-dinitr obenzene (1a), 1,2-dinitrobenzene (2a), and 2,3-dinitrotoluene (3a). T he fast displacement of one of the NO2 groups at 20-degrees-C leads to the colored nitroarylthiolate (3b), nitroaryl disulfide (2c) ions, or nitroaryl mono- and disulfide ions (lb/lc) in equilibrium. In turn, 2 c slowly reacts with 2a affording bis (2-nitrophenyl) disulfide 2d by SNAr substitution. The comparison of the reaction rates of 2-nitrophen yl mono- and disulfide ions (2b, 2c) on 1,2-dinitrobenzene (2a) and fl uoro-2-nitrobenzene, and those of S (-1/3) ions on dinitroaromatics (1 a, 2a) and fluroro-2- or fluoro-4-nitrobenzenes reveals the highly nuc leofugality of the NO2 group with respect to fluorine, the best nucleo fuge of the halogens.