For the catalyst system of ruthenium and carboxylic acid, which is useful for the efficient tail-to-tail dimerization of acrylonitrile, the TON increases as the ruthenium catalyst concentration is decreased. Furthermore, the addition of aromatic solvents of equal volume to that of acrylonitrile improves the catalyst activity. Especially, the use of diphenyl ether leads to a 1.7 time improvement of the TON.
and carboxylic acid is useful for the tail-to-tail dimerization of acrylonitrile, proceeding without the formation of undesired by-product propionitrile. Carboxylic acids having pK a 3.5-5 are suitable as co-catalysts for the dimerization of acrylonitrile. The relationship between the logarithm of the relative rate in the dimer formation and the pK a of m- and p-substituted benzoicacids (Bronsted plot)