Polarography of salicylidenebenzohydrazide in solutions of varying pH at a dropping-mercury electrode: effect of hydrogen bonding

Abstract

The polarographic behaviour of salicylidenebenzohydrazide (SBH) at a dropping-mercury electrode was studied in aqueous Britton–Robinson buffers containing 40% ethanol. The polarograms consist each of one wave in acidic medium. The height of the wave decreases and its E_½ shifts to more negative potentials with increasing pH until it diminishes completely at pH > 10.7. At pH values > 7.2 a second wave appears, the height of which increases with pH and becomes developed at pH values > 10.7. In acid solutions 4-electrons are consumed in the reduction of CN. The second wave is attributed to the reduction of salicylaldehyde which is formed from the hydrolysis of the hydrazide. The effect of pH on the limiting current and E_½ as well as the reduction mechanism are discussed. The kinetic parameters of the electrode reaction are also determined.