Electrochemical behavior of copper ions and silver ion in hydracrylonitrile and some related nitriles

Abstract

The electrochemical behavior of copper ions in hydracrylonitrile and related nitriles has been investigated. It is of interest to note that in hydracrylonitrile copper(II) ion is solvated by the nitrile group, whereas in I:I alcohol-nitrile mixtures, it is solvated by the hydroxyl group. This unusual situation appears to be due to the fact that hydracrylonitrile (dielectric constant, 65), I:I ethanol-acetonitrile mixture (dielectric constant, 32), and. I:I I-butanol-propionitrile mixture are polar solvent systems and, therefore, favor the more polar solvated form of copper(II) ion. This, in- hydracrylonitrile has the solvent molecules oriented with the nitrile group attached to copper(II) ion and the hydroxyl group sticking out and forming a polar outer sheath and in I:I alcohol-nitrile mixture has alcohol rather than nitrile molecules in the co-ordination sphere. Nitrile-solvated copper(II) ion with an outer sheath consisting only of alkyl groups behaves like a non-polar solute. In view of the absence of any solvent effect on the potentials of the copper couples in hydracrylonitrile, 3-butenenitrile, and in the alkoxypropionitriles, copper ions are most likely solvated by the trans conformer of these solvents. The effect of substituents in the 3-position in propionitrile i.e., on the basicity of the nitrile group on the potentials of the copper couples, is consistent with the influence of the substituents on other functional groups in different compounds. Except for the fact that silver(I) ion is reduced at potentials more positive than those at which copper(I) ion is reduced, the electrochemical reduction of silver(I) ion in hydracrylonitrile and related nitriles is similar to that of copper(I) ion.