The interaction of isomeric dinitrobenzenes (DNBs) with titanium(III), tin(II), and vanadium(II) chlorides, which are reducing agents used as electron carriers in the electrosynthesis of diaminobenzenes, has been studied. Rate constants of the reduction of isomeric DNBs and nitrophenylhydroxylamines by SnCl2 and TiCl3 in a 2 M water-alcohol solution (10 vol.% C2H5OH) of HCl were measured, and activation energies of the reduction of isomeric DNBs were determined. The rates of interaction of DNBs with the listed mediators increase in the series SnCl2 < TiCl3 < VCl2. It is shown that the electrolysis of DNBs in the presence of an excess of these mediators makes it possible to obtain the corresponding diaminobenzenes with a yield of 60–90%.

Characteristics of LiClO4/TTG and LiClO4/DMF electrolytes at different salt concentrations have been experimentally determined by conductometry, Li-7, H-1, C-13 NMR. It has been demonstrated that the influence of these parameters on the oxygen reaction is due to solvation and electrical conductivity, which, determine the transport characteristics of the reaction participants. In DMF the formation of Li2O2 proceeds predominantly through the solution bulk. In TTG the reaction proceeds predominantly on the electrode surface and does not depend on LiClO4 concentration, which is likely due to the formation of Li2O2 on the electrode surface without passing into the solution bulk with a weak concentration dependence of LiClO4 dissociation in TTG. It cannot be ruled out that the LiClO4 concentration in TTG has an effect on the oxygen reduction mechanism at higher concentrations (> 2 M) because of the complex formation. At any LiClO4 concentration in TTG, the amount of electricity in the cathodic process is lower and the reaction reversibility is higher than in DMF solutions. The key factor responsible for the change in the characteristics of the oxygen reaction in TTG is the decrease in the electrical conductivity and diffusion coefficients of O-2 and Li+ with increasing concentration, due to the viscosity of the solution and low dielectric constant. (c) 2021 Elsevier Ltd. All rights reserved.

The necessity of the studying of carbonaceous materials differing in their surface area and structure is called for by the fact that these materials are used until now in the designing of positive electrodes for lithium-oxygen current sources. Under the model conditions, the effect of some factors on the effectiveness of oxygen reduction reaction at the positive electrode is studied. Among them are: properties of the dimethylsulfoxide- and acetonitrile-based electrolytes, the carbonaceous material (ХС 72, Super P, and carbon nanotubes) structure and its relevant transport processes depending on the electrode active layer mass (thickness) and the polarization current density, which determines the oxygen reaction effectiveness at the carbonaceous material. The electrochemically active surface area is shown to increase with the specific surface area, which is determined by the carbonaceous material porous structure, its mass at the electrode, the solvent properties, and the reaction rate. The active layer thickness and current density must be chosen for each carbonaceous material individually, depending upon its structure. At that, the active layer entire surface must be electrochemically accessible; it must make possible the lithium peroxide formation and subsequent decomposition. In the dimethylsulfoxide-based electrolyte (high donor number), the oxygen reduction reaction is highly reversible; the lithium peroxide formation here occurs via disproportionation in the solution bulk and results in the formation of Li 2 O 2 particles with disordered (in all probability, toroidal) structure. This facilitates the back reaction (Li 2 O 2 anodic decomposition), in good agreement with literature data [1]. In acetonitrile-based electrolyte (low donor number), the oxygen reduction reaction occurs in adsorbed state, producing LiО 2 that disproportionates at the electrode surface forming a lithium peroxide insulating film whose oxidation needs high overvoltage. On the strength of all the parameters, carbon nanotubes are most effective in the oxygen reduction reaction in the dimethylsulfoxide-based electrolyte, because the carbon nanotubes have large volume of mesopores for the reactant transport, high electrochemically active surface area for the Li 2 O 2 accumulation, and thus provide high characteristics per electrode.

Polarographic behavior of 2,4-dinitrobenzene and products of its reduction, 2-chloro-5-nitroaniline and 4-chloro-3-nitroaniline, is studied: it is shown that formation of the corresponding chloronitroanilines in the case of polarographic reduction of 2,4-dinitrochlorobenzene is rather problematic. 0.1 M NaOH is recommended as the supporting solution for analytical control of conversion of 2,4-dinitrochlorobenzene and a mixture of 2-chloro-5-nitroaniline and 4-chloro-3-nitroaniline in reaction solutions obtained by preparative electroreduction of 2,4-dinitrochlorobenzene.

Electrochemical behavior of 2,4-dinitrochlorobenzene was studied using the method of preparative electrolysis in an acidic medium. The effect of the cathode material, temperature, nature of the solvent, concentrations of the initial dinitro compound and hydrochloric acid on the current efficiency of chloronitroanilines and their ratio was studied. Conditions of electrosynthesis of chloronitroanilines with predominant content of 2-chloro-5-nitroaniline (72–76 %) in the reaction solutions are found providing the yield of chloronitroanilines of 83–86% and the current efficiency of about 100%.

The electrochemical behavior of a complex of cobalt with dimethylglyoxime Co(DMG) 2 (H 2 O) 2 is studied by cyclic voltametry. Peaks corresponding to redox transitions Co(III)/Co(II) and Co(II)/Co(I) are observed in the potential region 0.4 to −1.8 V (Ag/AgCl). The product of reduction of the initial complex interacts with carbon dioxide to form a stable compound, probably an intermediate product of electrocatalytic reduction of CO 2 to CO in the presence of N 4 -macrocyclic complexes of cobalt.

Two methods of preparation of 4-aminodiphenylamine (I) are compared: by electrochemical reduction of an alkaline solution of 4-nitrosodiphenylamine (II), extracted from a technological solution, and by electrolysis of the solution itself, which contains, apart from the nitroso compound, methanol and NaCl. By voltammetry and preparative electrosynthesis it is shown that the lower reduction rate of the technological solution of the Na salt of II is due to inhibiting effects of methanol and NaCl. Tetraalkylammonium cations, decreasing the limiting reduction current of II, do not affect the electrosynthesis rate when the generated I is continuously extracted into a water-immiscible solvent.

Conditions for the production of N-tert-butyl-2-benzothiazolesulfenamide (TBBS) in an oxidative condensation of 2-mercaptobenzothiazole and tert-butylamine are determined. The electrosynthesis occurs during electrolysis of a 4.5–5.0 M NaCl solution containing a water-immiscible organic solvent extracting TBBS. The process efficiency is the highest at the following conditions: a 1 : 8 ratio between 2-mercaptobenzothiazole and tert-butylamine, a DSA, a stainless-steel cathode, a current density of 300 A m–2, and a continuous extraction of TBBS into a 3 : 1 mixture of carbon tetrachloride and acetonitrile. Under these conditions, the TBBS yield is 98–100%, the current efficiency is 74%, the process productivity is 0.9 kg m–2 h–1, and the electricity consumption is 1.9 kW h kg–1. Repeated use of the aqueous phase corrected for the source products jeopardizes neither the process characteristics nor the product quality.

An approximately 20-% alkali solution remains after the electroreduction of an alkali solution of a sodium salt of 4-nitrosodiphenylamine (II), in the course of which the formed 4-aminodiphenylamine (I) is continuously extracted into a water-immiscible solvent. The remaining solution, which contains about 10 mM I and up to 1 mM II, may be used for preparing the catholyte for another experiment. To this end, the solution must be anodically treated using a stainless-steel electrode, and the charge spent in the treatment must equal that spent during the electroreduction. After the treatment, the solution settles; the content of II remains virtually unchanged, that of I drops about tenfold, and that of alkali is 50% of the calculated (1 F per mole of alkali). A multiple use of the same alkali solution makes no impact on the yields of I.

Conditions for the synthesis of 4-aminodiphenylamine (I) by electroreducing a 1 M solution of a sodium salt of 4-nitrosodiphenylamine (II) in a 5-% alkali solution are found. The electroreduction is carried out on the copper and stainless-steel cathodes with a continuous extraction of the product into a water-immiscible solvent. Variations in the alkali concentration, current density, and temperature have no effect on the yield of I, which is almost quantitative. The current efficiency increases with the temperature and approaches 60% at 60–70°C on a copper cathode. Copper and stainless-steel cathodes and stainless-steel anodes are sufficiently stable in the 4-aminodiphenylamine electrosynthesis.

The electroreduction of technological solutions of a sodium salt of 4-nitrosodiphenylamine with a continuous extraction of formed 4-aminodiphenylamine into a water-immiscible solvent and a separation of the latter, leaves a solution containing alkali, sodium chloride, methanol, and admixtures of the initial and target compounds. Freed from the methanol, the solution may serve as anolyte in the salt electroreduction, instead of an alkali solution used for the purpose. The most suitable anode material is titanium covered with platinum or iridium. Anodically treated solutions are colorless and contain no initial and target substances but include oxygen compounds of chlorine. The formation of the compounds may be avoided by introducing 10 –4 M Co 2+ into solution. The ions may be used repeatedly.

The various derivatives of 2,2,6,6-tetramethylpiperidine and their. stable nitroxyl radicals were investigated by means of chemical, electrochemical and empirical calculation methods. The titration results were calculated by means of TURBO BASIC with PKAS and MINIGLASS algorithm, and the prototropic experimental data were obtained. The reaction ways were calculated on the basis of the formation enthalpie values which were calculated by means of AM 1 (MOPACK) method. On the basis of a voltammetry and an electrolysis under controlled potential the reaction products were analyzed and the yields of the investigated processes were received. The various quasi-reversible redox reactions of the type stable nitroxyl radical double left right arrow oxoammonium cation were investigated by means of a cyclic voltammetry and electrochemical impedance spectroscopy. The mechanisms of the investigated reactions have been discussed and the reaction schemes are presented.

The effect of 4-aminodiphenylamine (I) on the electroreduction of 4-nitrosodiphenylamine (II) is studied by the voltammetric method at stationary copper and platinum electrodes. The conclusion that the electroreduction of II is inhibited by I is drawn on the basis of the following: the directly proportional dependence of the current on the concentration of II is violated, the current decreases with time at a constant potential and with an ordinal number of the experimental run conducted without renewing the electrode surface, the current also decreases upon adding I. It is shown that I partially desorbs from the surface of the electrode kept in solution at potentials insufficient for the I formation. The reaction rate remains the same if an organic solvent miscible with the aqueous phase and dissolving I is introduced to the phase. The inhibition effect can partially be eliminated by elevating the temperature.

Electrochemical behavior of tert-butyl-2-benzothiazolesulfenamide (I), one of the powerful promoters of the rubber vulcanization process, is studied. It is shown that I is not oxidized anodically at dimensionally stable anodes, platinum, and platinum- or iridium-coated titanium and is not reduced at the stainless steel and platinum cathodes. At a dropping mercury electrode in an acid media containing I, a cathodic wave with E-1/2 of about -0.2 V is observed. The wave is attributed to the reduction of corresponding mercury mercaptide formed in the preceding chemical reaction between I and mercury. With an increased concentration of I, a second wave with E-1/2 Of about -0.4 V appears, which is related to adsorption of sulfur-containing products on mercury and complications in the reduction at such an electrode. One more wave, caused by the catalytic hydrogen evolution, emerges at potentials more negative than -1.2 V.

A procedure for the polarographic determination of 4-chloroaniline and 4-chloronitrobenzene simultaneously present in solution was developed. The procedure is based on recording the reduction waves of 4-chloronitrobezene and the Schiff base formed by 4-chloroaniline and salicylic aldehyde in a buffer solution with pH 1.80. The determination limits are 2.5 x 10(-3) M for 4-chloronitrobezene and 5.1 x 10(-3) M for 4-chloroaniline; RSDs are no more than 4 and 6%, respectively.

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