Monomer/polymer Schiff base copper(II) complexes for catalytic oxidative polymerization of 2,2′‐dihydroxybiphenyl

Catalytic oxidative polymerization of 2,2′‐dihydroxybiphenyl (DHBP) was performed by using both the Schiff base monomer‐Cu(II) complex and Schiff base polymer‐Cu(II) complex compounds as catalysts and hydrogen peroxide as oxidant, respectively. The dependence of monomer conversion and molecular weight distribution on various reaction parameters, including time, temperature, solvent as well as the amount of catalyst and oxidant were investigated. The structure of the poly‐2,2′‐dihydroxybiphenyl (PDHBP) was confirmed by UV‐vis, IR, ¹H and ¹³C NMR spectroscopy techniques. The electrochemical and thermal properties of PDHBP were also studied. DSC data revealed that PDHBP was amorphous. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2977–2984, 2009     

过氧化氢水溶液催化氧化环戊烯制备戊二醛

用过氧化氢水溶液氧化环戊烯制得戊二醛。对多种催化剂-溶剂体系进行了试验, 在钨酸-叔丁醇体系中得到了最高的戊二醛得率: 近60%(30%过氧化氢水溶液为氧化剂)或80%(50%过氧化氢水溶液为氧化剂)。同时, 对该反应的机理进行了初步研究, 提出环戊烯被过氧化氢氧化为戊二醛是经过环氧化物中间产物的观点。     

Activation of Hydrogen Peroxide by Ionic Liquids: Mechanistic Studies and Application in the Epoxidation of Olefins

Imidazolium‐based ionic liquids that contain perrhenate anions are very efficient reaction media for the epoxidation of olefins with H₂O₂ as an oxidant, thus affording cyclooctene in almost quantitative yields. The mechanism of this reaction does not follow the usual pathway through peroxo complexes, as is the case with long‐known molecular transition‐metal catalysts. By using in situ Raman, FTIR, and NMR spectroscopy and DFT calculations, we have shown that the formation of hydrogen bonds between the oxidant and perrhenate activates the oxidant, thereby leading to the transfer of an oxygen atom onto the olefin demonstrating the special features of an ionic liquid as a reaction environment. The influence of the imidazolium cation and the oxidant (aqueous H₂O₂, urea hydrogen peroxide, and tert‐butyl hydrogen peroxide) on the efficiency of the epoxidation of cis‐cyclooctene were examined. Other olefinic substrates were also used in this study and they exhibited good yields of the corresponding epoxides. This report shows the potential of using simple complexes or salts for the activation of hydrogen peroxide, owing to the interactions between the solvent medium and the active complex.     

Monolayers of salen derivatives as catalytic planes for alkene oxidation in water

Monolayers at the gas/water interface have been used as an adjustable catalytic system in which the molecular density may be modified. Mn(III)-salen complexes bearing perfluoroalkyl substituents have been organized as a Langmuir film on an aqueous subphase containing a urea/hydrogen peroxide adduct (UHP, the oxidant) and cinnamyl alcohol (the substrate). The catalytic activity of the monolayer for the epoxidation of the alkene dissolved in water has been demonstrated and the reaction kinetic investigated. For a constant area per molecule of catalyst, the reaction rate exhibits first-order dependence on oxidant concentration and zero-order dependence on alkene concentration, in agreement with the reaction orders reported for Mn(III)-salen-catalyzed epoxidation reactions carried out in solution. Furthermore, kinetic experiments suggest an enhanced activity of the catalysts assembled in a Langmuir film relative to that observed in bulk reaction. Finally, varying the molecular density of the catalyst at the gas/water interface highlights an important dependence of the catalytic activity of the layer with the mean molecular area. A strong increase of the catalytic properties of the monolayer was observed for a mean molecular area of 140-145 A2, an increase which was supposedly related to a modification of the Mn(III)-salen complex orientation at the interface upon compression. This hypothesis was supported by PM-IRRAS (polarization modulation infrared reflection adsorption spectroscopy) experiments performed in situ on the monolayer. Such results demonstrate that a soft and adjustable molecular system like a Langmuir film can be used to better understand the reactivity in various heterogeneous and/or pseudohomogeneous (such as those based on dendrimers) catalytic systems.     

NaY型沸石分子筛催化环己胺氧化制备环己酮肟

考察了系列氧化剂、催化剂和溶剂对环己胺液相氧化制备环己酮肟的影响,发现以乙腈为溶剂,过氧化氢为氧化剂,NaY型沸石分子筛对该反应具有优良的催化性能。 对该反应体系进行了五因素四水平的正交实验,确定了适宜的催化剂用量、溶剂用量、反应时间、反应温度和氧化剂用量,比较分析了各因素对环己胺转化率和环己酮肟选择性的影响。 确定了环己胺液相氧化反应的最佳工艺条件为：环己胺为3 mL,催化剂为03 g,环己胺、溶剂和氧化剂的体积比为1∶3∶3,65 ℃反应2 h。 讨论了环己胺液相催化氧化的反应机理。     

Stationary Kinetics of Light Olefin Oxidation by Hydrogen Peroxide in Aqueous Alkali Solutions in the Presence of Fe(III) Oxide

The steady-state kinetics of ethylene and propylene oxidation by hydrogen peroxide in the presence of Fe(III) oxide in aqueous solutions with the permanent adding of H₂O₂ to the reaction medium was studied. The use of an original method for the study of the steady-state reaction kinetics with gas chromatographic detection of substrate consumption from the gas phase made it possible to estimate the apparent rate constants of ethylene oxidation, the ratio of the rate constants of propylene and ethylene oxidation, the reaction orders with respect to the substrate and oxidant concentration, the dependence of the apparent rate constant of ethylene oxidation on the catalyst weight and on the pH of solution, and the apparent activation energy of the process under condition of substrate distribution between the gas and liquid phases. It was found that the kinetic isotope effect in ethylene oxidation is almost absent when completely deuterated ethylene is used.     

Selective oxidation of alcohols to aldehydes by hydrogen peroxide using hexamolybdochromate(III) as catalyst

Anderson type hexamolybdochromate(III) was utilized as a catalyst for facile conversion of various aliphatic, benzylic and heterocyclic alcohols to corresponding aldehydes and ketones in good yields. The reaction was carried out in 50% aq. acetonitrile using hydrogen peroxide as the oxidant at 50 °C. The reaction was found to involve oxidation of the catalyst to its active Cr(V) intermediate by hydrogen peroxide.     

Zirconium oxide complex‐functionalized MCM‐41 nanostructure: an efficient and reusable mesoporous catalyst for oxidation of sulfides and oxidative coupling of thiols using hydrogen peroxide

Zirconium oxide complex‐functionalized mesoporous MCM‐41 (Zr‐oxide@MCM‐41) as an efficient and reusable catalyst is reported for the oxidation of sulfides into sulfoxides using hydrogen peroxide (H₂O₂) as the oxidant, with short reaction times in good to excellent yields at room temperature under solvent‐free conditions. Also, a simple and efficient method is reported for the oxidative coupling of thiols into corresponding disulfides in good to high yields using H₂O₂ as oxidant in the presence of Zr‐oxide@MCM‐41 as recoverable catalyst in ethanol at room temperature. A series of sulfides and thiols possessing functional groups was successfully converted into corresponding products. After completion of reactions the catalyst was easily separated with simple filtration from the reaction mixture and reused for several consecutive runs without significant loss of catalytic efficiency. The mesoporous catalyst was characterized using Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area measurements, X‐ray diffraction, transmission and scanning electron microscopies, energy‐dispersive X‐ray spectroscopy and thermogravimetric analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

Redoxmethoden mit neutronenaktiviertem Silbermetall (110mAg) als Radioreagenz

A new analytical method using metallic silver (^110mAg) as radioreagent is reported. A known amount of excess oxidant is applied to the reducing agent which is to be determined. After the reaction has taken place, the excess of the oxidizing agent is reacted with the neutron-activated silver whereby^110mAg ions are released. The count rate of the solution is proportional to the excess of the oxidant, thus it is possible to determine the original content of the reducing agent in question. The proposed redox procedure based on back measurements has been applied to determinations of hydrogen peroxide, sodium oxalate, potassium ferrocyanide(II), uranium(IV), as well as hydroquinone and ethanol in the μg range. The method makes use of calibration curves; the standard deviation is ±2% on the average. Necessary heights of the normal potentials of the involved systems, favourable reaction conditions, and kineticsa are discussed.

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Herrn Prof. Dr. Hans Lieb zum 80. Geburtstag gewidmet.     

过氧化环己酮对二苯并噻吩的氧化脱硫研究

二苯并噻吩（dibenzothiophene DBT）及其衍生物是重油、减压馏分油及渣油中的主要硫化物。在通常的加氢脱硫中，二苯并噻吩系列是较难脱除的一类有机硫。近年来，以二苯并噻吩系列为模型的深度脱硫研究发展迅速。李建源等对二苯并噻吩及其衍生物为模型的氧化脱硫（Oxidative desulfurization ODS）、加氢脱硫、吸附脱硫及生物脱硫等作了较为详尽的报道。     

Oxidative radical cyclization on enamide systems using n-Bu3SnH and dilauroyl peroxide

Efficient 5-endo and 6-endo oxidative radical cyclizations on enamide systems are described using nBu₃SnH and dilauroyl peroxide both as initiator and oxidant. Dibenzoyl peroxide and dicumyl peroxide were also tested in the same reaction and the product yields were very similar to those obtained with dilauroyl peroxide. The erythrina ring system was constructed in a two-step sequence featuring this novel process.     

环氧环戊烷的无溶剂合成工艺

以聚苯乙烯-二乙烯苯接枝磷钨酸季铵盐为三相相转移催化剂,以H2O2为氧化剂,KCl为助催化剂,研究了环戊烯(CPE)合成环氧环戊烷(CPEO)的无溶剂工艺。 讨论了催化剂和助催化剂用量、反应温度、反应时间、环戊烯与H2O2摩尔比对反应的影响。 确定了无溶剂环氧环戊烷合成反应的条件为(以0.056 mol H2O2计)：催化剂1.0 g、助催化剂0.025 g、反应温度40 ℃、反应时间5 h、n(CPE)∶n(H2O2)=2.1∶1.0。 CPEO的平均收率约为96%。 催化剂回收重复使用6次活性无明显降低。     

Efficient and convenient oxidation of organic halides to carbonyl compounds by H2O2 in ethanol

Various primary and secondary organic bromides were oxidized by hydrogen peroxide in refluxing ethanol to give the corresponding aldehydes/and ketones in high yield up to 94%; organic chlorides were oxidized to the corresponding aldehydes/and ketones by the same oxidant in ethanol in the presence of 10 mol % of KBr as the catalyst.     

Kinetic studies on the reaction of N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetate chromium(III) with hydrogen peroxide

The rate of reaction of Cr(III)L (L=N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetate) with hydrogen peroxide was studied in aqueous media and was found to yield Cr(VI) over the temperature range of 25–41 °C. The reaction was followed spectrophotometrically at 396 nm under pseudo-first order conditions with hydrogen peroxide in a large excess. The reaction follows first-order kinetics in Cr(III). The dependence of the rate constant on hydrogen peroxide concentration is attributed to the formation of an intermediate between the monohydroxy chromium(III) complex and hydrogen peroxide which decomposes in the rate determining step. At high hydrogen peroxide concentration, the order is changed from first to zero order.The values of the intramolecular electron transfer rate constant, the formation constant of the intermediate complex and the activation parameters were calculated.     

功能化酸性离子液体催化柴油氧化脱硫的研究

以功能化酸性离子液体为催化剂,30%双氧水为氧化剂,将加氢柴油中的含硫化合物氧化为相应的砜类物质,并用N-甲基吡咯烷酮（NMP）萃取一次。同时考察了反应温度、反应时间和催化剂用量等因素对氧化脱硫反应的影响,得出最佳反应条件为,3mL油样（硫的质量分数为200×10-6）、1.5g酸性离子液体、 0.3mL H2O2、 25℃,3.5h、VNMP/Vdiesel=1∶1,脱硫率可达到86.7%,柴油硫的质量分数仅为25×10-6左右,反应结束后,可通过简单的倾倒将油样和催化剂分离,重复使用5次,其催化活性变化不大。     

Formation and dissociation equilibria of intermediate species in the oxidation of cobalt(II)-dipeptide complexes

Summary The oxidation of various cobalt(II)-dipeptide complexes in the presence of both molecular oxygen and hydrogen peroxide is examined. The nature of the oxidant exercises a marked influence on the reaction path. The oxo-intermediate species formed apparently possesses different structures, depending on the oxidant. Moreover, when molecular oxygen is employed, the inertness of the resulting cobalt(III)-dipeptide complexes is much higher, suggesting a different degree of protonation. The effect of the ligand structure on the oxidative process is considered; the reaction rate is found to be strongly influenced by the hydrophobicity of the substituent group and by the presence of amidic hydrogen.     

Kinetics and mechanism of water catalytic oxidation by a Ru3+(bpy)3 complex in the presence of colloidal cobalt hydroxide

Kinetics of the catalytic oxidation of water to molecular oxygen by a tris(bipyridyl) Ru(III) complex is studied in the presence of colloidal cobalt hydroxide stabilized by starch. Oxidant consumption follows the first-order rate law with respect to the oxidant concentration. The dependence of the apparent rate constant of this process on the catalyst concentration, initial oxidant concentration, and initial concentration of its reduced form was determined. The dependence of the oxygen yield on H⁺ at pH 7–11 and a catalyst concentration of 10-⁷-10-³ mol¹ is studied. An intermediate product of the reaction was found, which is probably a bridged peroxo complex of cobalt. The kinetic scheme and mechanism of the reaction is proposed, which agree with experimental observations.     

Chemiluminescence (CL) emission generated during oxidation of pyrogallol and its application in analytical chemistry. I. Effect of oxidant compound

An investigation of chemiluminescence (CL)-emission generated by the oxidation of pyrogallol using various inorganic oxidant compounds is reported in this F.I.A.-merging zone application. The oxidant compounds that showed measurable CL-emission were permanganate, periodate, hypochlorite anions, cerium(IV) and hydrogen peroxide. The different oxidant compounds showed CL-emissions at different pH-ranges. The CL-emission was limited by the inner filter effect and this was more intense for oxidants of selective oxidation. Kinetic effects were also found in the case of oxidation by permanganate. Plots of CL-emission against pH give evidence of speciation and or deactivation mechanism effects. The analytical parameters for the determination of the oxidants are given. Sensitivities of 895 600, 19 500, 33 723, 10 680 and 56 703 mV M(-1) were found for the determination of permanganate, cerium(IV), periodate, hypochlorite and hydrogen peroxide, respectively. The calibration curves of the oxidant determination were generally S-shaped; the S-shaped calibration curve of periodate was closer to a straight line relationship while that of hypochlorite was almost a straight line; detection limits in the range of 10(-4) M oxidant concentration were found for nearly all oxidants. The analytical parameters for determination of pyrogallol by the CL-emission generated through oxidation by the different oxidants at optimum conditions were 1.16x10(6) mV M(-1) for permanganate; 0.086x10(6) mV M(-1) for cerium(IV); 0.91x10(6) mV M(-1) for periodate; 0.012x10(6) mV M(-1) for hypochlorite; and 0.25x10(6) mV M(-1) for hydrogen peroxide. The detection limit was 1.0x10(-4) M. The nearly straight-line relationship (initial part of the plot) for CL-emission with oxidant concentration gives an indication that the CL-reaction of pyrogallol oxidation by hypochlorite proceeds through a process that involves energy transfer while the pronounced S-shaped curve produced by permanganate gives the indication that the reaction proceeds through a process that does not involve energy transfer according to the mathematical model of CL-emission that controls the F.I.A.-merging zone technique of the flow apparatus used in this work. The sequence of completeness of the oxidation process by each oxidant was MnO(4)(-)>H(2)O(2)>IO(4)(-)>OCl(-); the stoichiometric quantity of the oxidant per pyrogallol molecule for the rapid part of the overall oxidation by each different oxidant was attempted; this is an index-value of the oxidation state of the fluorescent excited molecule. Finally, the impact of the above findings for further analytical applications is discussed.     

Effect of gold nanoparticle as a novel nanocatalyst on luminol-hydrazine chemiluminescence system and its analytical application

In this work the catalytic role of unsupported gold nanoparticles on the luminol–hydrazine reaction is investigated. Gold nanoparticles catalyze the reaction of hydrazine and dissolved oxygen to generate hydrogen peroxide and also catalyze the oxidation of luminol by the produced hydrogen peroxide. The result is an intense chemiluminescence (CL) due to the excited 3-aminophthalate anion. In the absence of gold nanoparticles no detectable CL was observed by the reaction of luminol and hydrazine unless an external oxidant is present in the system. The size effect of gold nanoparticles on the CL intensity was investigated. The most intensive CL signals were obtained with 15-nm gold nanoparticles. UV–vis spectra and transmission electron microscopy studies were used to investigate the CL mechanism. The luminol and hydroxide ion concentration, gold nanoparticles size and flow rate were optimized. The proposed method was successfully applied to the determination of hydrazine in boiler feed water samples. Between 0.1 and 30 μM of hydrazine could be determined with a detection limit of 30 nM.     

Synthesis,characterization, and catalytic activity of a polymer-supported copper(II) complex with a thiosemicarbazone ligand

A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates including alkenes and alcohols using H₂O₂ as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out.