Acrylonitrile was allowed to react with three substituted hydrocarbon 1,3-dienes, namely, 2,3-dimethyl-1,3-butadiene (DMB), 4-methyl-1,3-pentadiene (MPD), and Isoprene (IF) in 1,2-dichloroethane in the presence of various amounts of zinc chloride at different temperatures, Alternating copolymers and [4 + 2] cycloadducts formed spontaneously. The structure of the diene and its electron-rich character control the product distribution, In the reaction of DMB and AN, raising the temperature and increasing the ZnCl2 concentration enhance the cycloaddition process, while the maximum yield of the copolymerization is at 45 degrees C; At higher temperatures, no copolymers formed. With MPD, only copolymer is formed because the two terminal methyl groups preclude the concerted [4 + 2] cycloaddition. IF is less reactive than DMB, and. the overall yields are lower. These results are in agreement with a postulated mechanism involving competition between a pi-allyl 2-hexene-1,6-diradical and concerted cycloaddition. A II-transfer mechanism is suggested to explain the lack of copolymer for DMB/AN or IP/AN;at higher temperatures and ZnCl2 concentrations.