The Reduction of Substituted Nitrobenzenes at the Dropping Mercury Cathode

Abstract

Substituted nitrobenzenes were among the first organic compounds to be investigated using the polarographic technique. The early work was performed by the Japanese, Shikata and his co-workers, and from this work Shikata and Tachi3 formulated the "electronegativity rule of reduction potentials," i. e., that organic compounds are more easily reduced as more electronegative groups are substituted in the same molecule.These investigators measured the reduction potentials by the tangent method us. the normal calomel electrode. This method of measurement deviates from present practice. I t was felt desirable to extend their investigations of substituted nitrobenzenes and to determine the relative effect of the position of the substituent upon the reduction process.The ortho-, meta-and para-isomers of nitrobenzoic acid, dinitrobenzene, nitrochlorobenzene, and nitrotoluene were selected for study. The reduction of these compounds a t the dropping mercury cathode from carefully buffered solutions over the PH range 2 to 14 was investigated to determine the nature of the reduction process and the effect of the position of the substituent groups upon the half-wave reduction potential. ExperimentalAll of the compounds investigated were obtained from Eastman Kodak Company and were further purified before use. Water solutions of 0.002 M concentration of oand m-nitrobenzoic acids and of 0.001 M concentration of

Effect of the surface roughness of conducting polypyrrole thin‐film electrodes on the electrocatalytic reduction of nitrobenzene

“…It could be seen that there was a distinct peak appearing at the −500 mV (SCE) region, and the cathodic current at this potential increased with the increase in the concentration of nitrobenzene. Thus, the cathodic peak current at −500 mV was associated with the reduction of nitrobenzene; this was in agreement with electroreduction potential reported for this reactant 31…”

“…Thus, the cathodic peak current at À500 mV was associated with the reduction of nitrobenzene; this was in agreement with electroreduction potential reported for this reactant. 31…”

Dopant induced effect on electrocatalytic reduction of nitrobenzene using conducting polypyrrole thin film electrodes

“…It could be seen that there was a distinct peak appearing at the −500 mV (SCE) region and the cathodic current at this potential increased with the increase in concentration of nitrobenzene. Thus, the cathodic peak current at −500 mV is associated with the reduction of nitrobenzene, which is in agreement with electro‐reduction potential reported for this reactant 41–43…”

Organic Polarography

“…The substituents make the reduction of nitrobenzene more difficult in the following order: nitro > carboxyl > chloro > methyl. Nitro and carboxyl show a greater effect in the ortho and para position than in the meta, whereas chlorine and methyl which increase the electron density at the ortho and para positions make the meta more easily reduced (3). The values reported by these investigators (3) differ from those reported by Pearson {31) by 0.25 to 0.35 volt.…”