Sulfur Vulcanization of Simple Model Olefins, Part I: Characterization of Vulcanization Products of 2,3-Dimethyl-2-Butene

Abstract

To study the mechanism of the sulfur vulcanization of rubber, 2,3-dimethyl-2-butene (C₆H₁₂) was used as a simple, low-molecular-weight model alkene. Only equivalent allylic positions are present in this alkene. Treating C₆H₁₂ with a mixture of ZnO, S₈, and the accelerator tetramethylthiuramdisulfide at 140°C yields a mixture of addition products (C₆H₁₁—S_n—C₆H₁₁). RP-HPLC in combination with MS and ¹H-NMR shows that the products differ only in the length of the sulfur bridge. Small quantities of isomerized products have been found, in which a 1,3-shift of the double bond has occurred.