Effect of proton donors and proton acceptor on the Polarographic reduction waves of o-,m- and p- nitrophenol in methanolic media

ABSTRACT

The polarographic behaviour of o, m- and p-nitrophenol is studied in methanolic solutions. Due to the poor proton availability of this medium reduction of part of the depolarizer proceeds with the uptake of the necessary protons from the other part. The anions thus formed are reduced along a second, more negative wave. This conclusion was supported through study on the effect of addition of acid proton donors [mono-and poly percent weak and strong acids], basic proton donors [e.g. [NH4]2CO3] or proton acceptor [e.g. NaOH]. The results were interpreted on the basis of Ruetschi and Trumpier's theory of H[+] ion impoverishment in the reduction layer. In presence of sodium hydroxide, reduction occurs in a single wave, at negative potentials, due to the ionization of the phenolic groups of the depolarizers. The difference in the behaviour of the three isomers is discussed