Organic Sulfides and Polysulfides. VI. Reactions of Metallic Oxides with Polysulfide Rubbers

1. Both mercaptides and disulfides were obtained by the reactions between benzyl mercaptan or tolyl mercaptan with zinc oxide or lead oxide. Qualitatively, mercaptides were formed from benzyl mercaptan easier than from tolyl mercaptan, and lead oxide reacted with mercaptan easier than zinc oxide with mercaptan. From the fact that no metallic sulfide was present, disulfides were likely formed from the oxidation of mercaptans by air. 2. The mono- or disulfides of the benzyl and tolyl series did not react with zinc oxide or lead oxide. 3. Neither tolyl tri- nor tetrasulfide reacted with zinc oxide, but benzyl tri- and tetrasulfide reacted with zinc oxide to give zinc sulfide. In the case of benzyl trisulfide, hydrogen sulfide, stilbene and benzaldehyde were formed, and in the case of tetrasulfide, we found the formation of hydrogen sulfide, stilbene, benzaldehyde and sulfur. 4. The tri- and tetrasulfide of both the benzyl and tolyl series reacted with lead oxide and they gave lead sulfide and organic disulfide. That is, they were desulfurized by lead oxide. In these reactions the benzyl series was more reactive than the tolyl series and the tetrasulfide was more reactive than trisulfide in the same series. 5. Lead oxide reacted with polysulfide easier than zinc oxide. 6. From the results of reactions between metallic oxide with mercaptan or other sulfide, it was concluded that the vulcanization mechanism of polysulfide rubber by metallic oxide is the reaction represented by Equations (1) to (4), the products being converted to high polymer without formation of a network of polysulfides.