The Alkaline Sulfide Reduction of Aromatic Nitro Compounds. VII. The Induction Period of the Sodium Monosulfide Reduction of Sodium m-Nitrobenzene Sulfonate

Abstract

Abstract In the sodium monosulfide reduction of sodium m-nitrobenzene sulfonate, an induction period appears. The present investigation was undertaken in order to determine the causes of this induction period. The induction period is due not to the nitro compound, but to the reducing agent. The induction period is shortened by means of irradiation by ultraviolet light, the addition of potassium persulfate, ferric chloride, and α,α′-azobisisobutyronitrile, or under atmospheric conditions. On the other hand, the addition of phenol or alcohol lengthens the induction period. Further, on the basis of polarographic and spectroscopic studies of the induction period, it has been suggested that soduim disulfide is produced during this induction period. On the basis of these data, it seems reasonable to assume that, in the reduction of aromatic nitro compounds by sodium monosulfide, the reducing power of monosulfide is very small in itself, and that the nitro group is reduced by the disulfide produced by the radical oxidation of monosulfide. The formation of the sulfide ion radical and its dimerization appear to be responsible for the induction period of this reaction.