ELECTROCHEMICAL REDUCTION OF P-CHLORONITROBENZENE IN DIPOLAR APROTIC-SOLVENTS CONTAINING CARBOXYLIC-ACIDS

The effect of carboxylic acids of different strength on polarographic behaviour of p-chloronitrobenzene in N,N-dimethylformamide has been in vestigated. In the presence of each acid a pre-wave appeared at a more positive potential than the original one, which was associated with t he cathodic reduction of a hydrogen-bonded adduct, formed between the nitrocompound and the acid molecules in the double layer of the electr ode. A linear correlation has been found between Delta E-1/2 and pK(HA )(DMF) (pK(HA)(DMF) refers to the value of the pK(a) measured in N,N-d imethylformamide, whereas Delta E-1/2 = E-1/2(pre-wave) - E-1/2(origin al wave)) Measurements in a solvent series in the presence of benzoic acid (BA) led to the correlation between Delta E-1/2 and PKBA (the sym bol PKBA denotes the value measured in a given solvent). The slopes of regression lines are discussed in terms of the double layer effect on the basicity of the -NO2 group.