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

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 E½ 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 C[double bond, length half m-dash]N. 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 E½ as well as the reduction mechanism are discussed. The kinetic parameters of the electrode reaction are also determined.