New proton donors in electrochemical mechanistic studies in non-aqueous solution dimethylsulfoxide: Chlorinated hydroxybenzonitriles

Chloroxynil (3,5-dichloro-4-hydroxy-benzonitrile) and 3-chloro-4-hydroxy-benzonitrile were found to be efficient proton donors in the electrochemical studies in aprotic solution. Their reduction appears at more negative potentials than the proton reduction in commonly used acids. They are demanded for protonation of species, which reduction appears negatively than the proton reduction of common strong proton donors. The ability to provide proton was tested on the reduction of ioxynil (3,5-diiodo-4-hydroxy-benzonitrile) in dimethylsulfoxide using tast polarography and controlled potential electrolysis. The height of the reduction wave of ioxynil increases in the presence of chloroxynil up to two electrons per molecule. Theoretical calculations also confirmed our conclusions.