Transformations of chloroethylenes in the presence of aprotonic acids

Abstract The cationic polymerization of vinyl chloride, vinylidene chloride, and cis ‐ and trans ‐ 1,2‐dichloroethylenes with the use of Lewis acid‐type catalysts has been studied. Vinylidene chloride is smoothly polymerized in the presence of ZnCl 2 at 40°C to form the dimer, 1,1,3,3‐tetrachlorobutene‐1, and poly(vinylidene chloride) having somewhat increased crystallinity (45%). Vinyl chloride is polymerized very slowly in the presence of AlCl 3 and TiCl 4 to give dimeric, trimeric, tetrameric, and low molecular weight polymer products. The polymerization is followed by carbonium ion isomerization that leads to reaction products of branched structure. The cis ‐ and trans ‐1,2‐dichloroethylenes react in the presence of AlCl 3 only at 50–60°C, and their polymerization is terminated at the stage of dimer and cyclic trimer formation. A mechanism of carbonium ion‐initiated polymerization of chloroethylenes is proposed, and the causes which lead to early termination of polymerization are discussed.