Electrochemical behaviour of some arylidene derivatives of carbohydrazide at mercury electrode in aqueous ethanolic buffer solutions

ABSTRACT

The electrochemical behavior of some arylidene derivatives of carbohydrazides was investigated by dc-polarography, de-polarography, cyclic voltammetry, and controlled potential coulometry techniques, at a mercury electrode in 50% ethanolic Britton-Robinson buffer solutions of pH 2-10. In acidic media [pH <4], the reduction occurs along a single irreversible 8-electron wave corresponding to the cleavage of the 2 N-N bonds and saturation of the 2 C=N centers, while at 6 <pH <8.5 the reduction takes placer through a single 4-electron wave leading to the saturation of the 2 C=N-centers only. In alkaline solutions [pH >/7] the total limiting current decreases on increasing the pH, this decrease is accompanied with the formation of a polarographic minimum till the wave disappears completely at pH's >10. The kinetic parameters, nature of the waves, the effect of pH on the limiting current and half-wave potentials as well as the reduction mechanism are discussed