A hydrocyanation process produces adiponitrile and other dinitriles having six carbon atoms. The process involves forming a reaction mixture in the presence of at least one Lewis acid. The reaction mixture includes ethylenically unsaturated nitriles having five carbon atoms, hydrogen cyanide, and a catalyst precursor composition. The reaction mixture is continuously fed while controlling the overall feed molar ratio of 2-pentenenitriles to all unsaturated nitriles and the overall feed molar ratio of hydrogen cyanide to all unsaturated nitriles. In the reaction product mixture, including adiponitrile, the ratio of the concentration of 2-pentenenitriles to the concentration of 3-pentenenitriles is from about 0.2/1 to about 10/1. Included in the catalyst precursor composition is a zero-valent nickel and at least one bidentate phosphite ligand.