Formation of radical-anions and radicals in the reaction of sodium sulfide with aromatic halogen compounds

The ESR and UV spectroscopic methods were used to establish the mechanism of the substitution of a chlorine atom by sulfide sulfur in the reactions of 2,5-dichloro-nitrobenzene (i) and p-dichlorobenzene (II) with sodium sulfide in N-methyl-2-pyrrolidone. The S2/sup -./ and S3/sup -./ radical-anions were detected and identified. The former corresponds to a narrow singlet with a g factor of 2.005 (λmax 440 nm), while the latter corresponds to a broad ESR signal with a g value of 2.028 (λmax 618 nm) [1-3]. The formation of the radical-anion of the reagent gave grounds for supposing that the reaction of (I) and (II) with sodium sulfide takes place through a one-electron transfer stage. Thus, a stable radical-anion characterized by hyperfine structure (hfs) (3/sub N/ x 2/sub H/ x 3/sub H/ x 3/sub H/ with constants of 11.6, 3.7, 3.5, and 0.7 Oe respectively) is formed in the nitrobenzene-sodium sulfide system