The hydrodimerization of acrylonitrile to adiponitrile is a commercial electrolytic process carried out in a narrow gap, undivided, bipolar cell and with a multiphase electrolyte. As a consequence of the process chemistry, the electrolyte contains oxygen, iron (III), and Pb(II) and the reduction of these species along with hydrogen evolution compete with the reduction of acrylonitrile at the cathode surfaces. This paper defines the cathode reactions which can occur and considers the influence of additives to the electrolyte and of pH changes induced by the cathode reaction itself on the relative importance of the competing electrode reactions.