The Polymerization of Acetonitrile in the Presence of Acidic and Basic Substances

Abstract Complexes of saturated nitriles with metal chlorides polymerize readily. In this paper, the polymerization of acetonitrile was carried out with more nitrile, than was needed to form the complex with metal chlorides. The conversion of the polymer increased in comparison with the case of the polymerization of the complex, indicating that the complex would partly dissociated in the reaction. The trimer of acetonitrile, 4-amino-2, 6-dimethylpyrimidine, was isolated, and ammonia was detected in addition to the brown polymer. The mechanism of the trimer formation in the presence of metal chlorides was illustrated through the removal of a proton from acetonitrile with the help of the chlorides, and through dimer formation. Hydrochloric acid and metaphosphoric acid were less active than metal chlorides. Ammonia itself was found to be inactive for the trimerization, bringing only acetamide. Water was also inactive in response to acetonitrile in the absence of acidic or basic substances. The derivation of ammonia was attributed to the decomposition of the pyrimidine compound and/or to the degradation of the polymer, but not to the hydrolysis of acetamide. The reaction of the polymer with propionaldehyde, the hydrolysis of the product, the carbylamine test, and a treatment of the trimer similar to that used for the complex suggested that the pyrimidine rings are involved in the polymer structure.