Spontaneous reactions of an electron-accepting substituted quinodimethane, 1-(2,2-dimethyl-1,3-dioxane-4,6-dione-5-ylidene)-4-(dicyanomethylene)-2, 5-cyclohexadiene, with p-substituted, alpha-substituted, and beta-substituted styrenes were investigated. When p-substituted styrenes were used as comonomers, no spontaneous reactions took place for styrenes with an electron-accepting p substituent such as COOMe and CN groups, and both terpolymers and cycloadducts were formed for the other p-substituted styrenes. When a-substituted and P-substituted styrenes were used as comonomers, no reactions occurred for alpha- and beta-substituted styrenes with a bulky phenyl group, and spontaneous reactions took place for those with a smaller methyl group. The reaction products were an alternating copolymer for a-substituted styrene and both terpolymers and 5-ethylidene-2,5-dimethyl-1,3-dioxane-4,6-dione for beta-substituted styrenes. The position of the methyl group in the styrenes significantly affected the product formation. This behavior in the spontaneous reactions was discussed on the basis of the ability of formation of the zwitterionic tetramethylene intermediate and its conformation, determined by polar and steric effects of the substituents in the substituted styrenes. (c) 2005 Wiley Periodicals, Inc.