Polarographic behaviour of some arylidene benzoic hydrazides in solutions of varying pH at the dropping mercury electrode

The polarographic behaviour of some arylidene benzoic hydrazides such as anisylidene benzoic hydrazide (ABH), furfurylidene benzoic hydrazide (FBH) and acetophenone benzoic hydrazide (Acet. BH) has been studied in universal buffer solutions containing 40% ethanol at the dme. In the pH range 3.7–8.1 the observed single reduction wave for all three compounds is assigned to the reduction of the ⪢ CN centre, whereas the ⪢ CO centre is inactive towards reduction due to the mesomeric effect of the neighbouring amino group. In alkaline media (pH 8.6) a second wave appears at a more negative potential due to the reduction of the corresponding aldehyde or ketone which is formed by hydrolytic decomposition of the molecule. The effect of pH on the limiting current and E1/2 as well as the reduction mechanism are discussed. The values of the kinetic parameters for the electrode reaction at different pH values are also computed from the polarographic results.