2,3-Dimethyl-2-butene (TME) was used as a model for polyisoprene in a study of zinc dimethyldithiocarbamate (Zn-2(dmtc)(4))-accelerated sulfur vulcanization. Mixtures of TME and curatives were heated in sealed tubes to 130 degrees C for various times and the contents analyzed by HPLC. Zn-2(dmtc)4, in the presence of sulfur, reacts with TME to form pendent groups of high sulfur rank. This reaction proceeds via a concerted mechanism without the formation of zinc perthiomercaptide as a true intermediate. Crossinking is slow but there is no induction period, the reaction between thiuram pendent groups of high sulfur rank being catalyzed by Zn-2(dmtc)(4). Tetramethylthiourea is not formed.