Halogenation par voie electrochimique de composes ethyleniques—II. Chloration du cyclohexene dans differents solvants nucleophiles

The electrochemical chlorination of cyclohexene has been studied in the same solvents (acetonitrile, N,N-dimethylformamide, dimethylsulfoxide and methanol) as those previously used for the bromination of this alkene.The oxidation peaks of the chloride ion are modified by addition of cyclohexene in a different way according to the solvent used. The simultaneous formation of mixed compounds with dichlorocyclohexane shows the solvents participation to the nucleophilic attack of the chloronium ion.     

Quantitative structure-property relationships of new benzoxazines and their electrooxidation as a model of metabolic degradation

The quantitative structure-property relationships study of 40 benzoxazines, that seem to be very promising antimycobacterial drugs, allowed proposing and testing of the equations describing effects of substituents on half-wave potentials of these compounds. Although two structural types of benzoxazines were studied (i.e. thioxobenzoxazinones and benzoxazinedithiones), it is possible to describe the effect of substituent on half-wave potentials of benzoxazines by one general equation. A good correlation for relationship between half-wave potential and energy of HOMO orbital was also found.The study of electrochemical oxidation of these compounds as a model of their possible metabolic degradation was performed. It was possible to propose general scheme of electrochemical oxidation of sulfur containing benzoxazine derivatives. From the metabolic point of view, desulfuration is the corresponding process to this pathway. As these derivatives were not examined in vivo, obtained results represent very beneficial clues, and, moreover, proposed scheme could serve as a support for the explanation of strong antimycobacterial activity of sulfur containing benzoxazines.     

Comparison of oxidation efficiency of disperse dyes by chemical and photoelectrocatalytic chlorination and removal of mutagenic activity

Degradation of Disperse Orange 1, Disperse Red 1 and Disperse Red 13 dyes has been performed using electrochemical oxidation on Pt electrode, chemical chlorination and photoelectrochemical oxidation on Ti/TiO₂ thin film electrodes in NaCl or Na₂SO₄ medium. 100% discoloration was obtained for all tested methods after 1 h of treatment. Faster color removal was obtained by photoelectrocatalytic oxidation in 0.1 mol L⁻¹ NaCl pH 4.0 under UV light and an applied potential of +1.0 V (vs SCE reference electrode), which indicates also values around 60% of TOC removal. The conventional chlorination method and electrochemical oxidation on Pt electrode resulted in negligible reduction of TOC removal. All dyes showed positive mutagenic activity in the Salmonella/microsome assay with the strain TA98 in the absence and presence of S9 (exogenous metabolic activation). Nevertheless, there is complete reduction of the mutagenic activity after 1 h of photoelectrocatalytic oxidation, suggesting that this process would be good option to remove disperse azo dyes from aqueous media.     

Investigation of the inhibitive effect of ortho-substituted anilines on corrosion of iron in 1 M HCl solutions

The inhibitory activity of some o-substituted anilines on iron corrosion in hydrochloric acid (HCl) was studied in relation to inhibitor concentration using potentiodynamic and electrochemical impedance spectroscopy (EIS) measurements. O-substituted anilines were found to act as mixed type inhibitors. The results showed that o-substituted anilines suppressed both cathodic and anodic processes of iron corrosion in 1 M HCl by its adsorption on the iron surface according to Langmuir adsorption isotherm. Potentiodynamic and EIS measurements reveal that these compounds inhibit the iron corrosion in 1 M HCl and that the efficiency increases with increasing of the inhibitor concentration. Data obtained from EIS are analyzed to model the corrosion inhibition process through equivalent circuit.     

Electrosynthesis in systems of two immiscible liquids and a phase transfer catalyst. VII. The chlorination of substituted naphthalenes

The chlorination of 12 substituted naphthalenes by electrochemical oxidation in CH₂Cl₂/H₂O emulsions containing a phase transfer reagent, Bu₄N⁺, is described. In all cases the major product can be a monochlorinated derivative, selectivity commonly 40–90%, but the efficiency and selectivity of the reactions depend on the nature and position of the substituent as well as the choice of electrolysis parameters. The anodic chlorination of naphthalenes has also been studied using cyclic voltammetry in CH₃CN and it is clear that the mechanism depends on the oxidation potential of the naphthalene.     

A single two electron transfer or high disproportionation: Electrochemical reduction of dinitrobibenzyl

Further electrochemical investigation and analysis of electrochemical data on 2,2′ and 4,4′-dinitrobibenzyl showed that these compounds reduce in two 1e steps with similar formal potentials. The disproportionation constants for 2,2′ and 4,4′-dinitrobibenzyl anion radicals as calculated from electrochemical data are 0.02 and 0.32 respectively.     

Untersuchungen zum anodischen Verhalten von Carbazolen und Indolo[3,2-b]carbazolen in Acetonitril

Investigations on the Anodic Behaviour of Carbazoles and Indolo[3,2-b]carbazoles The anodic oxidation of some substituted or condensed carbazole derivatives 1 – 6 has been investigated in acetonitrile using platinum electrodes. Substitution of the carbazoles in the 3-, 6-, and 9-positions prevents the anodic dimerization occurring otherwise in these positions. In these cases the electrochemical formation of stable cation radicals is possible. A stabilization of these anodie primary products and a decrease of the half-wave potentials is also effected by enlarging the π-electron system as in N-p-anisyl-dibenzo[e,g]carbazole 2 , in the indolo[3,2-b]-carbazoles 3 and in 9,9′-diphenyl-3,3′-dicarbazyl 4 . Due to the distortion of the C N-bonds neither a change of half-wave potentials nor a stabilization of the cation radicals by donor substitution or mesomeric effects has been observed in the case of N-p-anisylcarbazole 1 h , 1,4-bis-(9-carbazyl)-benzene 5 and 4,4′-bis-(9-carbazyl)-biphenyl 6 in comparison with N-phenyl-carbazole 1 e . The electrochemical preparation of 4 and the spectroscopical investigation of the cation radicals of some of the compounds are described.     

Nickel hydroxide electrocatalysts for alcohol oxidation reactions: An evaluation by infrared spectroscopy and electrochemical methods

We have investigated the electrochemical oxidation of four alcohols (methanol, 1-, 2- and tertiary butanol) at Ni hydroxide electrodes in alkaline electrolytes. In situ FTIR spectroscopy and electrochemical methods have been used to examine these oxidation reactions. Oxidation of the primary and secondary alcohols commences in the potential region where it is proposed that multi-layers of NiOOH are formed on the electrode surface; while no reaction occurs with tertiary butanol. Methanol oxidation occurs in two stages, with predominantly formate being formed in the potential window 0.36-0.44 V (vs. SCE), followed by further oxidation to carbonate at potentials above approx. 0.45 V. Butanoate is the only detected reaction product for 1-butanol electrooxidation in the potential range 0.36-0.5 V. The oxidation of 2-butanol is more complex. In the lower potential range (0.36-0.44 V) the major reaction product is butanone, which is further oxidised at higher potentials to either acetate or a mixture of propanoate and formate (or carbonate). In addition, rate constants have been determined for the first stage of the electrochemical oxidation of all the alcohols investigated.     

焦化废水氨氮去除方法的研究进展

焦化废水是煤制焦化产品回收过程中产生的废水,属于难处理的工业废水。文章就目前国内外针对焦化废水中氨氮的去除应用的各种物理化学方法,如蒸汽汽提法、吹脱解析法、离子交换法、折点氯化法、吸附沉淀法、电化学氧化法、催化氧化法等方法技术的原理及处理现状做出介绍,分析了各种处理方法的特点和出现的问题,并对处理焦化废水除氨氮做出展望。     

Effects of ultrasound on electrochemical oxidation mechanisms of p-substituted phenols at BDD and PbO2 anodes

The effects of low-frequency (40 kHz) ultrasound are investigated with regard to the effectiveness and mechanisms of electrochemical oxidation of p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) at BDD (boron-doped diamond) and PbO₂ anodes. Although ultrasound improved the disappearance rates of p-substituted phenols at both the BDD and PbO₂ anodes, the degree of enhancement varied according to the type of p-substituted phenol and type of anode under consideration. At the BDD anode, the %Increase values were in the range 73-83% for p-substituted phenol disappearance and in the range 60-70% for COD removal. However, at the PbO₂ anode, the corresponding %Increase values were in the range 50-70% for disappearance of p-substituted phenols and only 5-25% for COD removal, much lower values than obtained at the BDD anode. Further investigations on the influence of ultrasound on the electrochemical oxidation mechanisms at BDD and PbO₂ anodes revealed that the different increase extent were due to the specialized electrochemical oxidation mechanisms at these two anodes. The hydroxyl radicals were mainly free at the BDD electrodes with a larger reaction zone, but adsorbed at the PbO₂ electrodes with a smaller reaction zone. Therefore, the enhancement due to ultrasound was greater at the BDD anode than at the PbO₂ anode.     

5-氰基糖精的合成

磺酰脲类化合物具有很高的生物活性,在医药和农药上有非常广泛的应用。5-氰基糖精是制备5-取代糖精衍生物和5-取代苯磺酰脲类化合物的重要中间体。文章以对甲苯腈为原料,经氯磺化、氨解、氧化得到5-氰基糖精,总收率43.3%;产物及中间体经IR,1H NMR,MS确证结构。     

Electrochemical oxidation of oxalate ion in the presence of fluoride ion, and radical analysis by ESR

The problem at hand is the electrochemical oxidation of oxalate ion, which is accelerated by fluoride ion at a platinum anode. The hypothesis that fluoride ion traps incipient hydroxyl radicals as hydroxyfluoride radical anions was not supported by ESR experiments in which hydroxyl radicals were generated in the presence of the spin trap α-(4-pyridyl-1-oxide) N-tert-butyl-nitrone with and without the addition of fluoride ion. The electrochemical oxidation of oxalate at constant current followed current controlled kinetics both at a platinum anode, as observed previously, and at a boron-doped diamond anode, but the rate of the latter reaction was indifferent to the presence of fluoride ion. We propose that the competition of fluoride and hydroxide ions for the Pt/PtO_n surface inhibits the dimerization reactions that lead to oxygen evolution; the displacement of oxygen evolution to more positive potentials overcomes the overpotential for the oxidation of oxalate at this anode. Fluoride ion has no influence on the oxidation of oxalate at BDD because oxygen evolution inherently occurs at more positive potentials at this anode.     

Electrochemical oxidation of propylene utilising a thallium redox system

The oxidation of propylene in the presence of electrochemically regenerated thallium(III) was investigated over a range of electrode potentials. Polarisation curves made with the aid of a rotating platinum disc electrode, as well as current efficiencies for the formation of propylene glycol and acetone, are presented. At electrode potentials <2.2 V(E_H), product formation can be satisfactorily explained in terms of thallium(I) reoxidation. At higher electrode potentials, direct oxidation of the thallium-propylene complex as well as further electrochemical oxidation of the products so obtained must be postulated.     

BDD anodic oxidation as tertiary wastewater treatment for the removal of emerging micro‐pollutants,pathogens and organic matter

This work reports for the first time the removal of 17α‐ethynylestradiol (EE2), a synthetic estrogen hormone, from secondary treated effluents by electrochemical oxidation. Experiments were conducted in a single compartment reactor comprising a boron‐doped diamond (BDD) anode and a zirconium cathode. EE2, in the range 100–800 µg L^?1, was spiked in the post‐chlorination effluent of a municipal treatment plant and oxidized at 0.9–2.6 mA cm^?2 current density. Complete degradation of 100 µg L^?1 EE2 was achieved in 7 min at 2.1 mA cm^?2 and inherent conditions, while the addition of 0.1 mol L^?1 NaCl achieved removal in just a few seconds. The process was then tested in the pre‐chlorination effluent at 2.1 mA cm^?2 and inherent conditions; complete E. coli killing and EE2 removal occurred in just 1.5 and 3.5 min, respectively, while overall estrogenicity (assessed by the YES assay) and residual organic matter (in terms of chemical oxygen demand (COD)) decreased by 50% and 85% after 30 min, respectively. These results clearly show the potential of BBD electrochemical oxidation to serve as an efficient tertiary wastewater treatment. Copyright © 2011 Society of Chemical Industry     

Electrochemical studies of gold ore processing wastewater containing cyanide, copper, and sulfur compounds

The electrochemistry of real gold ore processing wastewater solutions from copper sulfide containing gold ore has been investigated. Analysis shows that the wastewater contains a range of sulfur compounds in various oxidation states from sulfide to sulfate. The electrochemical characteristics of the gold ore processing wastewater were evaluated using rotating disk, cyclic voltammetric, polarization and preparative electrolysis studies. The solutions show clear differences versus synthetic alkaline copper cyanide solutions. The copper cyanide/copper oxide catalysis normally seen in synthetic alkaline copper cyanide solutions is strongly inhibited. Two components of the wastewater solution identified as inhibiting the copper cyanide/copper oxide catalysis are copper sulfide complexes and thiocyanate. The inhibition of the copper cyanide/copper oxide catalysis appears to have an initiation time possibly related to the accumulation of copper-sulfur compounds at the electrode surface. The passivated surface is still able to oxidize cyanide, though at a maximum rate that corresponds to the limiting current for free cyanide assuming 1 electron per cyanide. The lack of the copper oxide coating that typically forms during oxidation of synthetic alkaline copper cyanide solutions, plus possibly the presence of various sulfur compounds, results in corrosion at higher anodic potentials when stainless steel is used as an electrode. However, stainless steel can be successfully used as an electrode material to treat the solutions if the potential is carefully controlled.     

Electrochemical assessment of electrochemical oxidation stability of self-assembled monolayers on gold and preparation of binary self-assembled monolayers on gold

Binary thiolates self-assembled monolayers (SAMs) on gold have been prepared efficiently by using an electrochemical oxidation combining with replacement reaction method. The electrochemical results show that both the SAMs of mercaptoacetic acid (MAA) and 1-dodecanethiol (DT) on gold surface are oxidized at certain anodic potentials (noting: it is not oxidative redeposition of alkanethiolate monolayers on gold surface), and the degree of electrochemical oxidation of single thiolates-SAMs is function of the polarization potential and polarization time. Therefore, formation of binary MAA-DT thiolates-SAMs can be achieved if MAA or DT is present in solution after the electrochemical oxidation of DT or MAA SAMs on gold electrode. In this case, the ratio of MAA to DT on the binary thiolates-SAMs can be easily controlled by controlling polarization potential and/or polarization time. The present approach enables us to prepare homogeneously binary SAMs with different composition, and assess the electrochemical oxidation stability of single thiolates-SAMs by means of cyclic voltammetry measurements of redox probe.     

氨氮废水处理技术综述

综述了氨氮废水处理技术的国内外研究现状,阐述了生物硝化反硝化法、反渗透法、氨吹脱法、化学沉淀法、离子交换法、电化学氧化法、折点氯化法去除氨氮的原理和影响因素,指出了各种方法的优、缺点及工艺技术的选择原则。     

Electrochemical impedance spectroscopic study of the intercalation of lithium and sodium ions into polyparaphenylene in carbonate-based electrolytes

Electrochemical impedance spectroscopy is used to investigate the electrochemical intercalation of lithium and sodium ions into polyparaphenylene under galvanostatic conditions in carbonate-based electrolyte. The evolution of the charge transfer resistance was studied at various selected potentials both during the reduction and the oxidation processes in order to control the stoichiometry of the intercalated compounds. The reversibility of the intercalation process, the effect of the cycling and the stability of the intercalated materials in the electrolyte as a function of the time were examined. A significant decrease of the charge transfer resistance occurs during the intercalation. That is related to an increase of the conductive state especially for the richest compounds Na_0.46(C₆H₄) and Li_0.50(C₆H₄).     

Oxidation Sequence of Sulfide Minerals in Operating and Out-of-Service Mine Waste Storage

To determine the oxidation sequence for sulfides in stored mine waste and to assess the effect of sulfide oxidation on the environment and the processing characteristics of anthropogenic deposits, the electrode potentials of sulfide minerals were measured in alkali solutions under conditions similar to storage conditions. The surface oxidation of sulfides was studied in relation to the nature and concentration of the dissolved gas. The influence of sulfide surface inhomogeneities and mineral concretion on the electrochemical oxidation was investigated. The oxidation rate of minerals was found to be increased by impurities with higher electropositive potentials.     

Electrochemical method for characterization of graphite-aluminium chloride intercalation compounds

The electrochemical behaviour of different graphites in molten lithium chloroaluminate electrolyte was studied using the potentiodynamic method. The oxidation currents observed at potentials below chlorine evolution are related to the oxidation of graphite during aluminium chloride intercalation.