Nucleophilic substitution of nitroaromatic halides by electrogenerated polysulphide ions in dimethylacetamide
Abstract
Electrogenerated polysulphide ions S˙3– and s82– readily react with haloaromatics, ArX, activated by nitro electron-withdrawing substituents in dimethylacetamide. Nucleophilic substitutions on fluoro-2,4-dinitrobenzene (1a; X = F), halo-4-nitrobenzenes (2a; X = F, Cl, Br, I) and 2-nitrobenzenes (3a; X = F, Cl, Br, I) lead to the coloured arylmonosulphide (1b; X = S–) and aryldisulphide (2c–3c; X = S2–) ions. From the reaction kinetics studied by UV–VIS spectrophotometry, the order of reactivity is ArF > ArBr, Arl > ArCl. The proposed SNAr mechanism implies that the dianions S62– and S82– are the nucleophilic agents (S62– S82–) rather than the S˙3– and S˙4– radical anions.