Earlier Parts of this series reported the partial separation and identification of the complex products of certain sulfur-olefin and related reactions chosen as models for examining the mechanism of vulcanization of natural and synthetic rubbers by sulfur. The main conclusion was that sulfur-olefin interaction proceeds by free-radical chain processes, and this has been quoted elsewhere and widely accepted. Results are now presented which extend and correct the earlier findings and lead to the different mechanistic conclusion that the reactions are polar in type, involving heterolysis of S—S and C—H bonds. This paper and Part XI deal with the products of the reactions of sulfur with mono-olefins and a 1,5-diolefin, respectively, and Part X presents a complementary kinetic investigation, the first for such reactions. All the experimental evidence is collated in Part XI in a general theory of sulfur-olefin interaction.

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When tert.-butoxy radicals react with mixed hydrocarbons, alkyl aromatic hydrocarbons are consumed more rapidly in mixtures with saturated hydrocarbons than would be expected from a knowledge of the reactivities of the components. This is due to a hydrogentransfer reaction, in which radicals from the saturated hydrocarbon attack the alkyl aromatic hydrocarbon. In experiments with deuterated toluene, it was found that methyl radicals abstract hydrogen from, and add to, the benzene ring as well as abstract hydrogen (deuterium) from the methyl group. These reactions render measurements of isotope rate factors difficult.