5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯的电分析特性研究

本文采用多种电化学方法研究了5-Cl-PADAT的电分析特性,求得了该化合物的电极反应电子转移数,扩散系数及电极反应标准速率常数,研究了其在滴汞电极上的吸附性质,提出了可能的电极还原过程。并且应用光度法测定了化合物的酸离解常数。     

Electrochemical Reduction of Nitrobenzene in Ionic Liquid BMImAc

Ionic liquid,1-butyl-3-methylimidazolium acetate（BMImAc）,was used in the electrochemical reduction of nitrobenzene.The electro-reduction of nitrobenzene on platinum electrode was studied by cyclic voltammetry（CV）,in situ Fourier transform infrared（FTIR） spectroscopy and constant-potential electrolysis.The experimental results show that electrochemical reduction process of nitrobenzene was controlled by diffusion,the main reduction product was azobenzen at-1.45 V,and the influences of scan rate and temperature on the electrochemical behaviors were obviously.A reduction mechanism of nitrobenzene in an ionic liquid was a probable ‘nitrobenzene→nitrosobenzene→azobenzene→aniline＇ main reductive reaction route.     

Electrocatalytic debromination of open-chain and cyclic dibromides in ionic liquids with cobalt(II)salen complex as mediator

The electrocatalytic reduction of open-chain and cyclic dibromides in ionic liquids, mediated by cobalt(II)salen, was investigated. Macro-scale constant-potential electrolysis in an undivided cell gave the corresponding debrominated products in moderate to good yields. The workup process after electrolysis proved to be much simpler in the ionic liquid than that in organic solvents. The possibility of reuse of the ionic liquid was demonstrated.     

Electrochemical oxidation of 2-thiouracil at pyrolytic graphite electrode

2-Thiouracil has been studied in phosphate buffers of pH 1.95-11.08 using linear and cyclic sweep voltammetry, coulometry, controlled potential electrolysis and spectral studies. One well-defined oxidation peak I(a) in the pH range 1.95-11.08 was noticed. The number of electrons involved in peak I(a) was found to be four in a thin layer cell whereas under exhaustive electrolysis condition oxidation was found to involve six electrons. A reduction peak II(c) (2e, 2H(+)) is noticed in the reverse sweep. Spectral studies during oxidation were carried out at different pH. Kinetic studies indicated that the decay of the UV-absorbing intermediate is a first order reaction. The products of the electrooxidation have been characterized and a tentative EC mechanism has been suggested for the oxidation of 2-thiouracil.     

硝基苯在离子液体BMimBF4-H2O中的电还原

采用循环伏安法和恒电位电解法研究了离子液体BMimBF4-H2O 中硝基苯在微铂电极上的电还原特性. 实验表明, 在BMimBF4中, 随着硝基苯和水的浓度变化, 循环伏安曲线的峰电位和峰电流呈现复杂的变化规律; 硝基苯在铂电极上的电还原反应为双分子8 电子3 步骤电化学过程, 第一步反应为准可逆单分子单电子转移步骤, 产生阴离子自由基, 第二步为2 电子转移步骤, 并伴有随后的双分子不可逆自由基偶合化学反应, 主要产物为氧化偶氮苯, 第三步是2 电子转移产生偶氮苯的过程.     

舒乐安定吸附伏安法的研究

Jimenez曾研究了舒乐安定的性质,但灵敏度较低,本文提出了测定痕量舒乐安定的吸附伏安法,在0.1 mol/L NH_3-NH_4Cl溶液(pH 9.3)中,富集电位—0.80 V(us. Ag/AgCl)得一灵敏的舒乐安定还原峰,Ep=—1.05 V,i_p与舒乐安定浓度在3.0×10~(-9)～5.0×10~(-6) mol/L范围内呈线性关系,检测限达1.0×10~(-9)mol/L,并用于试样的测定,用循环伏安法和恒电     

1,3-二甲基-5-亚硝基-6-氨基脲嘧啶铂电极电化学加氢机理研究

采用稳态极化法、循环伏安法和恒电位库仑法对1,3-二甲基-5-亚硝基-6-氨基脲嘧啶在铂电极上的电化学加氢机理进行了研究,研究介质为硫酸和硫酸钾水溶液.结果表明,pH=3时,1,3-二甲基-5-亚硝基-6-氨基脲嘧啶在铂电极析氢电位(-600～-800mV,vs.饱和硫酸钾的硫酸亚汞参比电极)前,发生加氢还原反应,氢离子在铂电极表面得到电子生成原子态的氢参与反应.随着pH值降低,加氢反应速度增大,还原电位正移.在铂电极上的电化学加氢过程受扩散控制,增大搅拌速度和提高温度都可提高反应速度.     

Electrochemical transformations of 4-(nitroaryl)-1,2- and -1,4-dihydropyridines in acetonitrile

The potentials of the electrolytic oxidation and reduction of 3,5-diethoxycarbonyl- 1,2- and -1,4-dihydropyridines with a nitroaryl substituent in the 4 position and their oxidized forms were determined by the method of a rotating disk electrode with a ring. The mechanism of the electrochemical oxidation of the starting dihydropyridines in acetonitrile on a graphite electrode was ascertained. The first step in the electrolytic reduction of the starting dihydropyridines is the addition of an electron to the nitro group to give anion radicals, the fine electronic structures and the hyperfine structure (hfs) constants of which were determined by EPR spectroscopy. The pyridinium fragment in the electrolytic oxidation products is reduced more readily than the nitro group in the aryl substituent.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1099–1105, August, 1985.     

Investigation of Electrochemical Behavior of Some Dithiophosphonates in Acetonitrile on the Platinum and Gold Electrodes

Some dithiophosphonate derivatives were synthesized and the electrochemical reduction mechanism was investigated by cyclic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry (CA) in 0.1 M tetrabutylammoniumtetrafluoroborate (TBATFB) in acetonitrile at platinum (Pt) and gold (Au) electrodes. Dithiophosphonates showed a cyclic voltammetric reduction peak at about ?1.1 V at Pt and ?1.3 V at Au electrode (vs. Ag/Ag⁺) in this media. It was also shown that dithiophosphonates can be determined quantitatively in acetonitrile using a calibration graph. The number of electrons transferred were calculated as 2 using ferrocene as a reference compound at the UME electrode. Mechanism of dithiophosphonates was also examined on Pt and Au electrodes and electrochemical reduction of dithiophosphonates seems to follow an EC mechanism with an irreversible electron transfer step. The reaction product in the bulk electrolysis experiment was isolated and identified using proton‐coupled P‐31 NMR, ¹³C‐NMR and IR spectroscopy. The adsorption tests for dithiophosphonates were revealed that no strong or weak adsorption phenomena exist on both Pt and Au electrodes. Simulation curves were acquired by DigiSim 3.03 version to investigate the reduction mechanism and to estimate the kinetic parameters for electrochemical and chemical steps.     

Electroreduction of a Binuclear Macrocyclic Complex of Copper(II) of the Robson Type in Aqueous Solutions

The electroreduction of a binuclear complex of copper(II) with a macrocyclic Schiff base of the Robson type on the basis of 4-tert-butyl-2,6-diformylphenol and 1,3-diaminopropane on the dropping-mercury, gold, amalgamated-gold, and glassy-carbon electrodes is studied in an aqueous environment. The data of experiments on preparative electrolysis and the results of measurements by a method of cyclic voltammetry and classic polarography suggest that the complex under study undergoes reduction in an aqueous environment with the transfer of four electrons with formation of copper(0) and a free Schiff base, which in conditions under investigation experiences hydrolytic decomposition.     

Electrochemical desulfurization of (1-adamantyl)(alkylsulfonyl)pyridines

The electroreduction of 4-(1-adamantyl)-2-(alkylsulfonyl)pyridines and 2-(1-adamantyl)-4-(tert-butylsulfonyl)pyridine was studied by polarography and preparative electrolysis on the mercury cathode at various compositions of the supporting electrolyte. Under the preparative electrolysis conditions, the C_Py-S bond is predominantly cleaved to form the corresponding adamantylpyridines. The conditions for selective electrochemical desulfurization were found. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 87–91, January, 2008.     

Electrochemical investigation of 2,2-dinitroethene-1,1-diamine (FOX-7) in aqueous media

Redox properties of 2,2-dinitroethene-1,1-diamine (FOX-7) were electrochemically investigated by DC polarography, cyclic voltammetry and preparative electrolyses, and electroreduction products were analysed. The polarographic reduction of FOX-7 in aqueous buffered solutions exhibited a total sum of limiting currents corresponding to the expected 18 electrons. This result fits well with the chemical reduction of this energetic material resulting in ethan-1,2-diamine. Exhaustive electrolysis, however, did not yield this product and the passed charge for total degradation of this compound corresponds only to 4–7 F. As the main products, gaseous N₂, N₂O, NO and NH₃ were proved by combination EC–GC–MS and, besides that, nitrite anions and ammonia ions were identified by other methods. All these observations suggest that instead of electrochemical reduction, an electrochemically initiated degradation process accompanying the exhaustive electrolysis occurs. This seems to be analogous to the chain of reactions during explosion, which are slowed down by a very low concentration and cooled by the solvent.     

Constant-potential electrolysis: determination of diffusion coefficients of thallium by using a hanging mercury drop electrode

The technique of constant-potential electrolysis at a stationary spherical electrode (hanging mercury drop) was investigated for the determination of the diffusion coefficient of Tl(I) in sodium citrate-sodium hydroxide medium and of Tl in mercury. Current-time curves, at controlled potential, were obtained, covering periods from 1 to 25 sec after the start of the electrolysis. The influence of applied potential, time of electrolysis, convection and shielding of the electrode was studied.     

Characterization of the Reduction of Oxygen at Anthraquinone-Modified Glassy Carbon and Highly Oriented Pyrolytic Graphite Electrodes

1-(N-Boc-aminomethyl)-4-(aminomethyl)benzene, bearing a protected amine group, was electrochemically grafted to glassy carbon and edge plane and basal plane highly oriented pyrolytic graphite electrodes by the oxidation of the corresponding linker. Following the removal of tert-butyloxycarbonyl protecting group, anthraquinone-2-carboxylic acid was coupled to the amine-terminated linker using solid-phase synthesis. The surface coverage of the immobilized anthraquinone redox centers was investigated by cyclic voltammetry and found to be the highest at edge plane and the lowest at the basal plane electrodes. The electrocatalytic activity of the anthraquinone-modified electrodes toward oxygen reduction was explored by cyclic voltammetry, chronoamperometry, and chronocoulometry at the unmodified and modified graphite electrodes. The immobilized anthraquinone was shown to catalyze the reduction of oxygen to hydrogen peroxide and the number of electrons transferred was two for all modified electrodes.     

The elementary stages of electroreduction of alkyl(hetero)arylsulfones in water-organic media

Intermediates (IM) of methyl(2-pyridyl)sulfone (MPS) and tert-butyl(2-pyridyl)sulfone (TBPS) formed upon the transfer of the first electron are studied by methods of laser photoelectron emission (LPE). The capture constants of solvated electrons by the MPS and TBPS molecules were determined. The time-resolved voltammograms of each sulfone measured in water-organic mixtures (20–80% ethanol or 60% DMSO) are found to demonstrate a redox wave with half-wave potentials E _1/2 = −1.34 and −1.37 V for MPS and TBPS, respectively. The dependence of rate constants for the one-electron IM reduction and oxidation on the potential is shown to obey the slow-discharge equation and the absolute magnitudes of rate constants are determined. The characteristic times of homogeneous transformations (decomposition, protonation) of MPS and TBPS radical anions do not exceed 3 × 10⁻⁷ s. The LPE data are compared with the results of preparative electrolysis and the mechanisms of both electrochemical and homogeneous reactions of IM are discussed.     

Metal complex electrocatalytic reduction of 1,1-dihalocyclopropanes

Catalytic electroreduction of several substituted gem-dihalocyclopropanes was studied in the presence of metal salen-complexes by polarography, cyclic voltammetry, and preparative electrolysis. Monohalocyclopropanes (54—59%) and the corresponding allene (5—9%) were the main reduction products. The reaction rate constants were determined. The inner-sphere electron transfer was shown to occur under these conditions.     

纳米TiO2膜修饰电极上对硝基苯甲酸异相电催化还原

有机电合成具有对环境友好、反应条件温和副产物少等优点并符合“原子经济性”要求，是一种可持续发展的绿色化学方法，已成为化学研究的重要前沿之一．使用媒质作为氧化剂和还原剂的间接电合成，大多为均相氧化还原电催化过程，把氧化还原催化剂固定在电极表面的异相电催化与均相催化相比具有更为显著的优点．本文采用循环伏安和电解合成法研究了纳米TiO2膜电极在硫酸介质和氢氧化钠介质中的氧化还原行为以及异相电催化还原对硝基苯甲酸的活性，探讨了纳米TiO2膜异相电催化的本质．     

Highly reactive σ-organonickel complexes in electrocatalytic processes

The electrochemical reduction of nickel complexes with 2,2′-bipyridine in the presence of ortho-substituted organic halides or white phosphorus yields the highly reactive σ-organonickel complexes. These complexes selectively react with organic halides forming cross-coupling products. The mechanism of these processes was investigated using the method of cyclic voltammetry and preparative electrolysis. The key intermediates of electrochemical functioning of white phosphorus in conditions of metallocomplex catalysis were detected.     

Dy(Ⅲ)离子在LiCl-KCl熔盐中的电化学行为及Dy-Ni金属间化合物的选择性制备

采用循环伏安、方波伏安和开路计时电位等电化学方法研究了Dy(Ⅲ)离子在LiCl-KCl 共晶盐中的电化学行为及Dy-Ni 合金形成的电化学机理. 循环伏安和方波伏安法研究表明, Dy(Ⅲ)离子的电化学还原过程为三个电子转移的一步反应. 与惰性W电极相比, Dy(Ⅲ) 离子在Ni 电极上的循环伏安曲线多出了三对氧化还原峰,是由于Dy与Ni 形成了合金化合物, 导致Dy(Ⅲ)离子在活性Ni 电极发生了欠电位沉积. 采用X射线衍射(XRD)和扫描电子显微镜(SEM)附带能量散射谱(EDS)对恒电位(-1.6, -1.8 和-2.0 V)电解制备的Dy-Ni 合金进行分析, 分别获得了DyNi₅, Dy₂Ni₇和DyNi₂金属间化合物. 实验结果表明, 通过控制电位进行恒电位电解可以有选择性地制备不同的金属间化合物.     

硝基苯在离子液体EMimBF4中的选择性电还原

采用循环伏安法和恒电位电解法研究了离子液体EMimBF4中硝基苯在微铂电极上的选择性电还原特性. 研究结果表明, 硝基苯在铂电极上的电还原反应为双分子八电子三步骤电化学过程: 第一步反应为准可逆单电子转移步骤, 产生阴离子自由基; 第二步为二电子转移步骤, 并伴有随后的双分子不可逆自由基偶合反应和快速质子化及脱水反应, 主要产物为氧化偶氮苯; 第三步是二电子转移产生偶氮苯的过程. 通过控制电位, 可以选择性地合成氧化偶氮苯和偶氮苯; 在EMimBF4中, 硝基苯和水的浓度变化对电化学行为产生较大影响.