Metal halide and organometal halide catalyzed copolymerization and cyclocodimerization of acrylonitrile and butadiene

The effect of inorganic halides MX (M = Zn, Al, Ti, B; X = Cl, Br) and organometallic halides MRX (M = Zn, Al; R = CH3; X = Cl) of LEWIS acid type was studied with respect to the copolymerization and the cyclocodimerization of acrylonitrile and butadiene. The relative acid strength of these halides was established by IR studies of the acrylonitrile/halide complexes. In the presence of these LEWIS acids, acrylonitrile cyclocodimerizes with butadiene to give 4‐cyanocyclohexene the yield of which increases with acid strength, e.g., 100% for BCl3. Some of these acids give rise to the simultaneous formation of an acrylonitrile/butadiene (1:1) copolymer. As the acid strength is increased, the copolymer yield passes through a maximum to become nil at the highest acid strengths (TiCl4, BCl3). Unlike the inorganic halides, the organometallic halides MRX give rise to spontaneous copolymerization. A general mechanism of the reactions in the presence of MX and MRX is postulated to account for the data obtained.