Linear Relationship between Activity of a New Ru-catalyst and Acidity of Substituted Benzoic Acids in the Dimerization of Acrylonitrile

Abstract

Abstract A new type of catalyst system using ruthenium 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 pKa 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 pKa of m- and p-substituted benzoic acids (Brønsted plot) was linear (R2 = 0.946) with a slope of −0.199. The role of the carboxylic acids can be considered to be effective protonation in the protonolysis of the carbon–ruthenium bond of an intermediate Ru complex.