Electrochemical Reduction Of Nitrobenzene Research Articles

Detection of nitrosobenzene as an intermediate in the electrochemical reduction of nitrobenzene on Ag in a flow reactor

Identification du nitrobenzene lors de la reduction electrochimique du nitrobenzene. Utilisation de la chromatographie HPLC couplee a un reacteur electrochimique a ecoulement

The electrochemical reduction of nitrobenzene and azoxybenzene in neutral and basic aqueous methanolic solutions at polycrystalline copper and nickel electrodes

The electrochemical reduction of nitrobenzene, azoxybenzene, azobenzene, phenylhydroxyl-amine and hydrazobenzene was studied at polycrystalline copper and nickel electrodes in neutral and basic aqueous methanolic solutions. Electronation of nitrobenzene, azo- and azoxybenzene was observed by voltammetry before the discharge potential of the medium whereas no wave obtained in the case of phenylhydroxylamine and hydrazobenzene. Under preparative electrolysis conditions, nitrobenzene gave a mixture of phenylhydroxylamine and aniline; the proportion of aniline increased when decreasing the potential even beyond the discharge potential of the medium and was larger at copper than at nickel electrodes. The reduction of phenylhydroxylamine to aniline under the same conditions did not go to completion. The reduction of azoxybenzene and azobenzene stopped at hydrazobenzene. An electrocatalytic hydrogenation mechanism is proposed for the reduction of phenylhydroxylamine to aniline. Aniline would be adsorbed on the surface and impede the catalytic process.

Electrochemistry of concentrated organic redox solutions

Electrochemical reduction of nitrobenzene (NB) at Pt microdisk electrodes (12.5 μm radius) is reported for solutions from 0.00026 to 1.0 mole fraction NB. In the absence of an inert solvent, e.g., acetonitrile, a well-defined current plateau is observed corresponding to the mass-transport limited reduction of undiluted NB. Limiting currents and diffusion coefficients are also reported for NB reduction in the following mixed solutions: NB/acetonitrile (NB mole fraction, χ NB = 0−1.0); NB/benzonitrile (χ NB = 0–0.65); and NB/toluene (χ NB =0.4–1.0). Maximum NB mass-transport limited reduction currents are observed at χ NB = 0.2, 0.4 and 0.6 in acetonitrile, benzonitrile, and toluene solutions, respectively. The resuls are discussed in terms of the combined effects of concentration, solution viscosity, and migration on limiting currents in concentrated redox solutions.

Raman spectroscopic observation of adsorbates on Ag during electrochemical reduction of nitrobenzene

Raman spectroscopic observation of the surface of a silver electrode during potentiostatic reduction of nitrobenzene in neutral and alkaline aqueous solutions has revealed adsorption of at least four chemical species at different potentials. At –0.5 V (vs. SCE), where the reduction starts, trans-azobenzene was detected with two other species. Raman bands of adsorbed aniline were observed at more cathodic potentials. When aniline was adsorbed from its aqueous solution, three of the above four species except azobenzene were detected on the electrode. Adsorbed aniline lies flat on the surface.

Raman spectra of adsorbates observed during electrochemical reduction of nitrobenzene

Raman spectra of adsorbates observed during electrochemical reduction of nitrobenzene

Raman spectra of adsorbates observed during electrochemical reduction of nitrobenzene

Surface enhanced Raman scattering (SERS) was applied to the study of a reaction system. When nitrobenzene was reduced at −0.5 V (versus SCE) on Ag in neutral and alkaline aqueous solutions, Raman bands of several adsorbates were observed on the electrode. One of them was assigned to trans-azobenzene by comparison to the solution spectrum. An experiment using nitrobenzene-d 5 supported the assignment. The adsorbate disappeared when the potential was changed to −0.7 V or more cathodic values.

Reduction electrochimique du nitrobenzene, en milieu micellaire aqueux, a divers pH. Influence de la nature des tensio-actifs

The electrochemical reduction of nitrobenzene has been studied in the presence of some anionic, cationic and non-ionic surfactants using a glassy carbon electrode or a dropping mercury electrode (polarography). The results are depending upon the electrode nature, the surfactant polarity and the pH of the solutions. On glassy carbon electrode and with cationic surfactants, the reduction is always a one step process for the totality of the studied pH scale (2–12). With the anionic and non-ionic surfactants, the potential is shifted towards the more negative values for a one step process or for a two step process, according to the pH value. For the polarographical studies, the electrochemical reduction of nitrobenzene is generally retarded by the presence of monomer surfactant molecules adsorbed on the mercury electrode, principally in acid media. In micellar solutions, the CTAB decreases the protonation rate of the nitrobenzene radical anion and facilitates the reduction by a dianion way. The anionic and non-ionic surfactants increase the radical anion stability and slow down the rate of the radical anion reduction.

Electrochemical Reduction of Nitrobenzene at Controlled Potentials

Electrochemical Reduction of Nitrobenzene at Controlled Potentials