Adsorption Of Nitro Compounds Research Articles

Thermally Activated Reactions of Nitrobenzene at the Ge(100)-2 × 1 Surface

The adsorption of nitro compounds on the germanium surface serves as a model system for understanding the formation of interfacial germanium oxynitride. We have studied the adsorption and thermal reactions of nitrobenzene on the Ge(100)-2 × 1 surface under ultrahigh vacuum conditions. A combination of infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption experiments together with density functional theory calculations was used to elucidate possible product structures and their associated reaction mechanisms. Our study suggests that nitrobenzene initially forms a 1,3-dipolar cycloaddition product with a Ge(100) surface dimer as the major species. Minor side products are also formed at 300 K. Upon heating, some of the adsorbates molecularly desorb, while a fraction of the adsorbates undergo oxygen atom insertion into the surface, transforming them into triplet nitrene products. The energetics and pathways of nitrobenzene on the Ge surface are discussed in comparison with those seen on the closely related Si(100)-2 × 1 surface, with some differences arising from the smaller adsorption energy of organic adsorbates on Ge.

Studies of electroreduction of nitropentane and nitrohexane on mercury electrodes in the presence of adsorbed aliphatic alcohols

AbstractElectroreduction of 1‐nitropentane and 1‐nitrohexane was studied on mercury electrodes in aqueous solutions, together with the inhibitors: n‐pentanol, n‐hexanol and n‐heptanol. The electrode behavior of these species was not found to be influenced by inhibitors at concentrations lower than 10 mM and 2 mM for n‐pentanol and n‐hexanol, respectively, because adsorption of nitrocompounds is stronger than that of alcohols. For high alcohol concentrations, when a total surface coverage by inhibitor molecules is almost achieved, the reaction of nitroalkanes is inhibited. Steric factors evaluated using the dependence of rate constant on inhibitor concentration were used in the determination of the orientation of reactant molecule on the electrode. For alcohol concentrations near saturation, the rate constant becomes independent of inhibitor concentration. In this case a reaction of nitroalkanes dissolved in the surface organic phase was postulated.

ChemInform Abstract: Infrared Spectroscopic Study of the Adsorption of Nitro Compounds and Amines on Cobalt Oxide.

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The Use of Differential Pulse and D.C. Polarography in the Analysis of Solutions Containing Surfactants

Abstract Peak currents in differential pulse polarography (DPP) are often used for quantitative analysis. In the presence of surfactants, peak currents depend not only on the concentration of the electroactive species, but also on that of the surfactant. In the presence of surfactants of biological origin, limiting currents obtained by d.c. polarography are often less sensitive to the effects of surfactants and are more suitable for quantitative analysis than DPP peak currents. Effects of surfactants on DPP curves were demonstrated for 4-nitrobenzoic acid in the presence of oligomers resulting from washing lignin preparations with water. In the study of adsorption of nitro compounds on lignin, d.c. polarographic curves yielded reliable adsorption isotherms whereas DPP peak currents indicated erroneously much stronger adsorption of nitro compounds on lignin.

Electrochemically oxidized carbon fibres as an adsorbent for the attachment of dissolved substances. Adsorption of nitro compounds and ion-exchange of heavy metals

The adsorption of several aromatic nitro compounds and the ion-exchange of heavy metal ions on electro-oxidized carbon fibres have been investigated using cyclic voltammetric and polarographic techniques. Electro-oxidation is performed by potentiostatic double pulse application. This procedure results in the generation of many functional —OH and —COOH groups with adsorptive and ion-exchanging properties.Multimolecular layers of adsorbed substances may be formed through a procedure of successive adsorption of the nitro-compound and electro-reduction to the corresponding amine, resulting in the attachment of considerable amounts of the nitro-compound to the carbon fibres.The ion-exchange capacity is estimated to be ca. 1 mequiv. g−1 and with slight deviations it follows the rank Ag, Cu, Cd, Pb, Hg. After the electro-reduction of the exchanged metal ions, the ion-exchange process can be repeated several times. This procedure is of importance for the removal of significant amounts of heavy and toxic metals from industrial waste waters. Key words: electro-oxidized carbon fibres, adsorption of aromatic nitro compounds, cation-exchange of heavy metals.

Adsorbed nitro-compounds and electron donor properties of magnesium oxide

The adsorption of nitro-compounds on the surface of MgO powder has been studied by e.s.r. and reflectance spectrophotometry. Radical anions are formed on clean MgO surfaces prepared in vacuo whereas this no longer occurs if the MgO surface is contaminated with water and carbon dioxide. Several possibilities for the source of electrons in MgO are discussed and it is suggested that some of the lattice oxygen ions on the surface may act as electron donors. The nitrobenzene radical ion appears to lie flat on the surface and the e.s.r. data indicate considerable rotational freedom at 20°C.