Electrochemical Reduction of Aromatic Ketones in N,N-Dimethylformamide Containing Benzoic Acid. Effect of the Basicity of the Carbonyl Group

The effect of benzoic acid on the polarographic reduction of a series of aromatic ketones in N,N- dimethylformamide has been investigated. In the presence of this acid a new cathodic wave (pre-wave) appears at more positive potentials than the original (orig.) wave of the reactant. A linear correlation has been found between ΔE½ and the pKBH+ values, where ΔE½ = E½ pre.wave -E½orig.wave and pKBH+ stands for the negative logarithm of the acidity constant of the protonated ketone . It is concluded that the pre-wave is associated with the cathodic reduction of a hydrogen-bonded adduct of 1 : 1 type formed between the carbonyl compound and the acid in the double layer. The effect of the double layer on the basicity of the ketones is discussed.