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用十二烷基硫醇在金电极表面形成自组装单分子层,采用循环伏安方法及扫描电化学显微镜对多巴胺在金电极和硫醇修饰电极上的电化学行为进行了研究,并考察了溶液pH及循环伏安扫描速度对多巴胺氧化还原过程的影响。结果表明,多巴胺能够渗透通过硫醇单分子层在电极表面发生氧化还原反应,修饰表面的存在对其氧化过程影响较明显。 相似文献
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用一种新型电极一PbO_2膜电极对木质素磺酸盐溶液进行电氧化反应,研究了溶液pH值、电解电压和电量对电氧化过程中木质素磺酸盐脱色反应的影响。结果表明,当电解电压维持在2.5V左右时能有效地使木质素磺酸盐发生脱色反应,高pH值条件有利于脱色反应的进行,电解电量的增加可提高脱色程度。 相似文献
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电催化氧化技术应用的关键问题之一在于寻找和研制开发催化活性高、导电性能好的阳极材料。采用电化学聚合法在硫酸钾溶液中制备了聚3,4-乙撑二氧噻吩膜修饰电极(PEDT)并通过自制的PEDT膜修饰电极首次对对苯二酚和邻苯二酚的电催化作用进行了探讨。 相似文献
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以奎宁为原料,经羟基氧化、开环、氨基Boe保护、双键臭氧氧化、醛基还原、羟基甲磺酰化后叠氮取代、叠氮基团的氢化还原及分子内环合等9步反应,合成了一种新的萘啶衍生物,即标题化合物.对其中关键的双键臭氧氧化和分子内环合的反应条件进行了研究,确定了较佳反应条件:双键臭氧氧化反应在-78℃下以臭氧为氧化剂、乙酸乙酯为溶剂;分子内环合反应以甲醇钠为碱、甲醇为溶剂,在65℃条件下反应12h.中间体及目标化合物的结构均经核磁共振氢谱、碳谱、质谱和元素分析进行确定. 相似文献
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Knotted ring polystyrene (PS) with molecular weight of 380 k was successfully synthesized by intramolecular cyclization reaction in cyclohexane under extremely diluted condition. Crude product was confirmed to include linear precursor molecule, single ring molecules, and various intermolecular-reacted byproducts by SEC and interaction chromatography characterizations. The crude product was fractionated repeatedly several times by high performance interaction chromatography and finally highly-purified knotted ring molecules were obtained. It has been found by SEC-MALS that the chain dimension of the knotted ring polymers is evidently smaller than those of linear and the trivial ring polymer, while knotted polymer molecules have the same absolute molecular weight as the corresponding counterparts. 相似文献
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An unsaturated adduct has been synthesized by the Diels-Alder reaction between resin acids and diallyl maleate. The obtained polymerizable product can be used both as monomer in the formation of allyl polymers and crosslinking agent. The monomer and its polymers were investigated by usual physical and chemical methods. The synthesized polymers present a linear structure, possibly associated with intramolecular cyclization at low molecular weights, or a three-dimensional structure at high conversions. They are fairly thermostable substances with carboxylic groups in the polymer chain. 相似文献
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Gold particles supported on carbon and titania were explored as catalysts for oxidation of CO or glycerol by O2 at room temperature in liquid-phase water. Although Au/carbon catalysts were not active for vapor phase CO oxidation at room
temperature, a turnover frequency of 5 s−1 could be achieved with comparable CO concentration in aqueous solution containing 1 M NaOH. The turnover frequency on Au/carbon
was a strong function of pH, decreasing by about a factor of 50 when the pH decreased from 14 to 0.3. Evidently, a catalytic
oxidation route that was not available in the vapor phase is enabled by operation in the liquid water at high pH. Since Au/titania
is active for vapor phase CO oxidation, the role of water, and therefore hydroxyl concentration, is not as significant as
that for Au/carbon. Hydrogen peroxide is also produced during CO oxidation over Au in liquid water and increasing the hydroxyl
concentration enhances its formation rate. For glycerol oxidation to glyceric acid (C3) and glycolic acid (C2) with O2 (1–10 atm) at 308–333 K over supported Au particles, high pH is required for catalysis to occur. Similar to CO oxidation
in liquid water, H2O2 is also produced during glycerol oxidation at high pH. The formation of the C-C cleavage product glycolic acid is attributed
to peroxide in the reaction. 相似文献
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Sara E. Davis Levi R. Houk Erin C. Tamargo Abhaya K. Datye Robert J. Davis 《Catalysis Today》2011,160(1):111
Supported Pt, Pd, and Au catalysts were evaluated in the aqueous-phase oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) at 295 K and high pH in a semibatch reactor. The intermediate reaction product 5-hydroxymethyl-2-furancarboxylic acid (HFCA) was formed in high yield over Au/C and Au/TiO2 at 690 kPa O2, 0.15 M HMF and 0.3 M NaOH, but did not continue to react substantially to FDCA at the specified O2 pressure and base concentration. In contrast, the final reaction product FDCA was formed over Pt/C and Pd/C under identical conditions. The initial turnover frequency of HMF conversion was an order of magnitude greater on Au catalysts compared to either Pt or Pd. Increasing the O2 pressure and NaOH concentration facilitated the conversion of HFCA to FDCA over the supported Au. The significant influence of base concentration on the product distribution indicates an important role of OH− in the activation, oxidation and degradation of HMF. 相似文献
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以组氨酸为原料,经选择性咪唑环氮的保护、氨基迈克尔加成、甲基化、关环、还原和消除等反应合成了标题化合物.对其中关键步骤氨基迈克尔加成反应和分子内关环反应进行了研究,获得了较优的工艺条件:在迈克尔加成反应中以甲醇钠为碱,甲醇为溶剂;在分子内环化反应中选择以叔丁醇钾为碱,四氢呋喃为溶剂.目标产物的总收率为28.3%,结构经1HNMR和MS进行了确证. 相似文献
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Gong-Jun Yang 《Electrochimica acta》2004,49(19):3121-3127
Based on the comprehensive analyses of the experimental results of the electrochemical methods, in situ UV-Vis absorption spectra, in situ electron spin resonance (ESR), and attenuated total-internal reflection (ATR) as well as the calculation of UV-Vis absorption data by PM3 Semi-Empirical method, a reaction mechanism for the redox processes of dobutamine was presented. When the anodic sweep is carried out, dobutamine firstly undergoes a free radical reaction with one-electron and one-proton to form semi-quinone free radicals, which will continuously convert to its corresponding quinone form by further electrochemical oxidation reaction. The formed quinone cannot only undergo a cyclization process by chemical reaction to produce a new compound, which can be reduced at more negative potential, but also be reduced to form dobutamine again when subsequent cathodic sweep is followed. The cyclization rate is depended upon pH values, and it increases with the increase of pH. In neutral medium, the corresponding oxidation form of the cyclization reaction product is easy to convert to melanin. 相似文献
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Y. P. Ting K. G. Neoh E. T. Kang K. L. Tan 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(1):31-36
The oxidation of the leucoemeraldine (LM) and emeraldine (EM) states of polyaniline (PAN) and the subsequent reprotonation and reduction of the nigraniline (NA) and pernigraniline (PNA) in acid gold solution were utilized for the spontaneous and sustained reduction of gold. The rate of Au reduction is strongly dependent on the intrinsic oxidation state of the polymer and the polymer surface area. The rate also increases with decreasing pH of the chloroauric solution to about pH ~ 1. X-ray photoelectron spectroscopic (XPS) results indicate that only elemental gold or Au(0) accumulates on the polymer surface. The N1s core-level spectra of the protonated and base form of EM films after Au reduction confirm that the intrinsic structure of the polymer remains intact. The process, however, is limited by the decreasing effective surface area of the polymer due to Au deposition. The results indicate that an LM film accumulated up to five times its own weight of Au (Au/monomer mole ratio > 2) before the recovery rate was significantly retarded. 相似文献
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《Journal of Sulfur Chemistry》2013,34(1-2):79-87
Based on an unexpected product isolated during the LDA-mediated intramolecular cyclization of a benzyl alkynyl sulfones, a conceptually new cyclization method for the formation of 5,6-dihydro-1,4-oxathiin S,S-dioxides is demonstrated. The reaction affords products with (het)aryl groups at the 5- and 6-positions in 7–54% yield. 相似文献