Redox Isomerism of α-Ferrocenylcarbenium Ions

The formation of α-ferrocenylcarbenium ions FcC⁺H₂ (λ_max 600 nm) and FcC⁺HCH₃ (λ_max 730 nm) and their redox isomerism at the protonation of ferrocenylmethanol and vinylferrocene was proved using the method of electronic spectroscopy. The effect on the process of the solvent and acid nature as well as of hydrogen peroxide additives is discussed.     

丙烯氧化反应的Redox机理

以流动床微分反应器研究了Bi_2MO_3O_(12)-Bi_2O_3催化剂上的丙烯氧化动力学。丙烯和氧的分压范围分别为0.05—0.95atm和0.07—0.80atm。当氧和丙烯分压低于0.30atm时, 丙烯醛的生成速度对丙烯为一级对氧为0.5级。表观活化能为30.1 kcal mol~(-1)。当丙烯和氧分压高于0.30atm时, 丙烯醛生成反应的动力学不能用幂速度方程描述。丙烯醛的生成速度对丙烯和氧分压存在着极大值。热脱附实验表明, 在低于150 ℃时, 分子态丙烯可以吸附于氧化态催化剂。但当温度高于300 ℃时, 丙烯则不以分子态吸附, 且脱附物为丙烯醛、一氧化碳和二氧化碳。在广阔的温度区(25—500 ℃)氧皆不以分子态处于催化剂上。因此, 建议了以表面双位反应为速控步骤的氧化还原机理。     

Redox deracemization of α-substituted 1,3-dihydroisobenzofurans

Chiral α-substituted 1,3-dihydroisobenzofurans are key scaffolds in a number of bioactive natural products and synthetic pharmaceuticals. However, catalytic asymmetric approaches have been rarely developed. Here, a redox deracemization technology is adopted to address the catalytic asymmetric synthesis. A broad range of α-aryl substituted 1,3-dihydroisobenzofurans are effectively deracemized in high efficiency with excellent ee. α-Alkynyl substituted ethers were also compatible with the deracemization technology.     

Ionic Liquid–Catalyzed Internal Redox Esterification Reaction

The internal redox esterification of α,β-unsaturated aldehydes and alcohols was carried out using different ionic liquids (ILs) as catalysts and reaction solvents. The basic ionic liquid, 1-butyl-3-methylimidazolium acetate ([bmim]OAc), exhibited the best activity for this reaction. The influences of the amount of ionic liquid catalyst and reaction time on yield of saturated ester have been investigated. The results showed that ionic liquid anions have a crucial effect on the redox esterification of α,β-unsaturated aldehydes and alcohols. The nucleophilic carbenes generated in situ from the ionic liquid cation were believed to be actual active species for this reactions.     

Redox Reaction of Disulfide/Polyaniline in Aqueous Solution

Introductionlthasbeensh0wnthat0rganodisulfidesIikeDMcTc0uldbep0lymerizedanddepolymerizedreversibly,correspondingtotheirchemical0reIectr0chemicaloxidati0nandreductionreactions.Thisisduetothereversibletbrmationandscissi0nofthedisulfidebond,atw0-electr0ntransferpr0cess(Schemel).LithiumsecondarybatterieswithatheoreticalenergydensityoflO7OWhjkgwereset-upusingtheabovedisulfidecompoundasthean0dicmaterial.H0wever,theredoxreacti0n0fdisulfidewasveryslowatr0omtemperature,thus,thechargeanddischargepro…     

Redox机理动力学内扩散影响的特征

在Pb_0.88Bi_0.06La_0.02Mo/SiO₂催化剂上,反应在动力学区域进行时,甲醇氧化制甲醛服从Redox机理动力学方程:r=(k₁k₂P甲醇Po₂)/(0.5k₁P甲醇+k₂Po₂)当催化剂颗粒增大至3mm时,内扩散影响严重,催化剂有效因子在0.38-0.73之间,其内扩散区域的速度方程为r内=(Do₂/RTKL)2φ_M[K(Po₂-Po_2.o)-ln(1+Kpo₂/1+Kpo_2.o)]^1/2测定了反应受O₂内扩散控制时的反应活化能E内为74.5kJ/mol。     

EuFeO3上CO氧化Redox机理动力学

ＥｕＦｅＯ３用柠檬酸络合法制备，ＥｕＦｅＯ３的钙钛矿物相用ＸＲＤ测定。用ＣＯ还原脉冲及用Ｏ２再氧化脉冲证实在ＥｕＦｅＯ３上ＣＯ氧化为Ｒｅｄｏｘ机理，用外循环流动无梯度反应器研究了ＥｕＦｅＯ３上ＣＯ氧化Ｒｅｄｏｘ动力学。实验结果服从Ｒｅｄｏｘ方程。用正交设计法估计动力学方程的参数。     

Redox sorption in metal–ion-exchanger nanocomposites upon electrochemical polarization

A conjugated macrokinetic problem is solved for two moving boundaries of chemical reactions during redox sorption in metal–ion-exchange nanocomposites under conditions of current flow. Numerical solutions to the multipoint boundary value problem indicate that the impact of the current includes a slowing of front migration associated with distinct stages of the chemical reaction between metal nanoparticles and oxygen due to electrochemical reduction, a reduced surface concentration of the active sorbate (oxygen), and an increased degree of redox sorption. An increase in the contribution from the electrochemical component and a transition to external diffusion control are observed as the current density grows.     

Redox Polymerization of Methyl Methacrylate in the Fluorous Triphasic System

Fluorous-phase chemistry is currently a topic of considerable interest1-6. Since fluoroustriphasic reactions were first described by the Curran and co-workers7, this triphasicsystem has been widely used for detagging7,8 and phase-vanishing reactions9-11. …     

Effect of Addition Groups on the Redox Properties of Fullerenes

采用循环伏安法和微分脉冲伏安法对比地研究了包括五种Ｃ６０的衍生物及四种Ｃ７０的衍生物的电化学性质．结果表明，推电子基团的引入使得富勒烯的氧化还原电位负移，这种负移的程度与加成基团的性质、个数和富勒烯的性质有关．对于Ｃ６０和Ｃ７０的单加成产物，负移的范围是０．０８～０．２０Ｖ．而对于Ｃ６０的双加成和三加成产物负移的范围分别为０．３０～０．３２Ｖ和０．５３～０．５８Ｖ．同时由于电位的负移大部分衍生物在低于＋１．５Ｖ（ｖｓ．ＳＣＥ）观察到了氧化峰，而Ｃ６０和Ｃ７０本身的氧化高达＋１．７Ｖ（ｖｓ．ＳＣＥ）．特别是对于Ｃ７０的双加成产物在＋０．４５Ｖ（ｖｓ．ＳＣＥ）出现了一个不可逆氧化峰，但是，对于同样加成基团的Ｃ６０双加成产物的氧化却在＋０．９０Ｖ（ｖｓ．ＳＣＥ），说明由于推电子基团的双加成引入，明显改变了Ｃ７０的电负性．     

Redox potentials of iron—nitrosyl complexes: DFT calculations

Quantum chemical calculations of the structure and solvation energies of mono- and dianions of Roussin’s red salt esters [Fe₂(μ-RS)₂(NO)₄] (R = Me, Et, Prⁱ, Bu^t) in solutions in THF and acetonitrile were carried out. In monoanions, an additional electron is localized on one Fe(NO)₂ fragment, which leads to significant structural distortion of the anion compared to neutral molecule. The second electron is localized on the other Fe(NO)₂ fragment; this causes symmetrization of the dianion geometry. There are good linear correlations between the calculated and experimental redox potentials of these systems. A relationship was proposed for estimation of the redox potentials of related iron—nitrosyl complexes. The standard redox potentials of the complex with R = Ph in water, DMSO, and acetonitrile evaluated using this expression lie between −0.5 and −0.6 V.     

REFeO~3上CO氧化Redox机理的控制步骤

用柠檬酸配合法制备REFeO~3 (RE=la, Pr, Nd, Sm, Eu, Gd, 及Dy)。用XRD测定了REFeO~3的钙钛矿结构。用CO还原脉冲及O~2氧化脉冲证实REFeO~3上CO氧化为Redox机理。用外循环流动无梯度反应器研究CO氧化稳态动力学。动力学方程中的参数用正交设计法估计。催化剂用CO还原的速率常数k~1比还原了的催化化剂用O~2再氧化速率常数k~2要大, k~1/k~2值在4.22～133之间, 这说明在REFeO~3上CO氧化的控制步骤为还原催化剂的再氧化。用脉冲法得到的CO转化率(X~C~O)比O~2的转化率(X~O~2)要大。脉冲法证实稳态动力学控制步骤的结论。Redox动力学方程式(9)可简化为控制步骤方程式(11)。催化剂还原速度常数与一定P~C~O及P~O~2下的反应速度呈近似的线性关系。在REFeO~3上CO氧化存在补偿效应。     

REFeO~3上CO氧化Redox机理的控制步骤

用柠檬酸配合法制备REFeO_3(RE=La,Pr,Nd,Sm,Eu,Gd,及Dy).用XRD测定了REFeO_3的钙钛矿结构.用CO还原脉冲及O_2氧化脉冲证实REFeO_3上CO氧化为Redox机理.用外循环流动无梯度反应器研究CO氧化稳态动力学.动力学方程中的参数用正交设计法估计.催化剂用CO还原的速率常数k_1比还原了的催化剂用O_2再氧化速率常数k_2要大,k_1/k_2值在4.22～133之间,这说明在REFeO_3上CO氧化的控制步骤为还原催化剂的再氧化.用脉冲法得到的CO转化率(X_(co)比O_2的转化率(X_o_2)要大.脉冲法证实稳态动力学控制步骤的结论.Redox动力学方程式(9)可简化为控制步骤方程式(11).催化剂还原速度常数与一定P_(co)及P_o_2下的反应速度呈近似的线性关系.在REFeO_3上CO氧化存在补偿效应.     

Studies on Redox Properties of Heteropoly Compounds Containing Rare Earth Elements

The redox properties of four series of more than one handred acids and salts of rare earth heteropoly compounds, such as LnHSiMoi2O40, In (PMo11 O39)211-, Ln (PW11 O39)211-, Ln (AsW11 O39)211-, Ln(GeW11O39)213-, Ln(BW11O39)215-, Ln(GaW11O39)216-, Ln(P2Mo17O61)217-, Ln (As2W17O61)217-, Ln2P2Mo18O62and Ln2HP2Mo17VO62(Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, etc. ) which have Keggin, Daw-son and their derivative structures, were studied by means of potentiometric titration, polarography and cy-clovoltammetry. The mechanisms of the redox reactions were supposed-and the orders of redox ability of the heteropoly compounds were concluded. The periodic changes in reduction potentials of Ln(PMo11O39)211-and Ln(P2Mo17O61)2217- with Ln atomic numbers, and the correlation between E1/2 of Ln(XMo11O39)2(?)-(X =P, Ge, Si) and nq2(n is the main quantum number of the central atoms and q is their charges) were found.     

Redox Conversions of Polyaniline in Composite Polyaniline–Nafion Polymer Films

Redox processes that occur in composite polyaniline–Nafion films formed on platinum or glassy carbon during the potential cycling are studied by radioisotope and electrochemical methods. Following a change in the conditions and range of potential cycling, the films exhibit a slow relaxation (memory effect).     

Redox induced translocation of a guest molecule between viologen-resorcinarene and β-cyclodextrin

Here we report the design of a three-component supramolecular system in which a guest molecule reversibly translocates between two macrocyclic hosts.     

Redox active, hybrid dendrimers containing Fréchet- and Newkome-type blocks

A new series of dendrimers was prepared by covalently attaching a Newkome dendron, a Fréchet dendron, and a redox active, aminoferrocene group to a central triazine core. Growth of the Newkome dendron has a more pronounced effect on the half-wave potential for the one-electron oxidation of the ferrocene residue than growth of the Fréchet dendron. All dendrimers show reversible or quasireversible voltammetric behavior at scan rates in the range 0.10-2.0 V s-1.     

How Do Redox Groups Behave around a Rigid Molecular Platform? Hexa(ferrocenylethynyl)benzenes and Their “Electrostatic” Redox Chemistry

A new family of hexakis(ferrocenylethynyl)benzenes was synthesized by Negishi coupling from ethynylferrocenes and C₆Br₆ and can be reversibly oxidized to stable hexaferrocenium salts (see picture, Ar^F=[3,5‐C₆H₃(CF₃)₂]). Their cyclic voltammograms show a single six‐electron wave, three distinct two‐electron waves, or a cascade of six single‐electron waves, depending on the electrolyte counterion and number of methyl substituents on the ferrocenyl groups.

     

Visualizing Redox Chemistry: Probing Environmental Oxidation–Reduction Reactions with Indicator Dyes

One of the important questions in the chemistry of pollutant degradation is the identity and distribution of chemical agents that are responsible for reduction reactions in the environment. Reduction occurs primarily in water-saturated environments, such as sediments, soils, and sludges. Redox indicators can be used (i) as chemical probes to obtain fundamental insights into biogeochemical processes and (ii) as the basis for demonstrations suitable for teaching aspects of environmental chemistry. This paper explores the latter with examples that involve a variety of indicators (indigo sulfonates, resazurin, etc.), environmental media (anaerobic sediments and granular iron metal), and physico-chemical processes (oxidation-reduction, adsorption, and diffusion). The results show that reduction by either media (sediments or iron metal) is primarily, although not always entirely, a surface reaction. This situation results in indicator behavior that is interesting and challenging for students with a wide range of backgrounds.