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排序方式: 共有125条查询结果,搜索用时 31 毫秒
101.
102.
Nicholas A A Rossi Robert M Anderson Richard G Jones Simon J Holder 《Polymer International》2004,53(4):465-471
ABA block copolymers of styrene and methylphenylsilane were synthesized using a methodology based on 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-mediated controlled free radical polymerisation. Samples of α,ω-dihalo(polymethylphenysilane) were reacted with a hydroxyl derivative of TEMPO to give suitable macroinitiators for the controlled (‘living’) free radical polymerisation of styrene. The polymerisation of styrene was carried out in bulk at 130 °C. Block copolymers were characterised using size exclusion chromatography and 1H and 13C NMR spectroscopy. Copyright © 2004 Society of Chemical Industry 相似文献
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以2-乙基己醇作为原料,O_2作为氧化剂,无碱参与下催化氧化合成2-乙基己酸。使用气相色谱(GC)进行定量分析,气质联用仪(GC-MS)进行定性分析。考察了催化剂、溶剂、反应温度、时间及氧压力对反应的影响。结果表明:2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)/硝酸铜为合适的催化剂体系,乙酸乙酯为合适的溶剂。适宜的反应条件是:催化剂TEMPO用量为2-乙基己醇物质的量的5%、硝酸铜用量为2-乙基己醇物质的量的4%,100℃、0.5 MPa O_2压力下反应6 h,2-乙基己酸收率可达77.1%。O_2恒压条件下该反应是拟一级反应,反应活化能为59.9 k J/mol。主要副产物是3-庚醇和3-庚酮。 相似文献
105.
Wei Zhang Shiping Yang Zengming Shen 《Advanced Synthesis \u0026amp; Catalysis》2016,358(15):2392-2397
A novel method for the synthesis of cyanomethylated tetrahydroisoquinolines has been developed with mild reaction conditions, good yields and a broad substrate scope. Acetonitrile, a common solvent, is for the first time used as a pronucleophile for this type of two sp3 C−H bonds cross‐dehydrogenative coupling (CDC) reaction. A new oxidative system (CuCl2/TEMPO/Cs2CO3) has been established by our group, in which the mild TEMPO reagent was found to be a highly efficient oxidant.
106.
J. Z. Praskalo‐Milanovic M. M. Kostic S. I. Dimitrijevic‐Brankovic P. D. Skundric 《应用聚合物科学杂志》2010,117(3):1772-1779
The purpose of this research was to accomplish antimicrobial properties in lyocell fibers by Ag+ ions sorption from aqueous silver nitrate solution. Sorption properties of lyocell fibers were improved by the selective TEMPO‐mediated oxidation, i.e. oxidation with sodium hypochlorite and catalytic amount of sodium bromide and 2,2,6,6‐tetramethylpiperidine‐1‐oxy radical (TEMPO). The most suitable experimental conditions for the selective TEMPO‐mediated oxidation were determined by changing oxidation conditions: concentration of sodium hypochlorite, as well as duration of sorption. The obtained results showed that the maximum sorption capacity (0.809 mmol of Ag+ ions per gram of fibers) of modified lyocell fibers was obtained for the sample modified with 4.84 mmol NaClO per gram of cellulose, during 1 h. The antifungal activity of the TEMPO‐oxidized lyocell fibers with silver ions against fungi from the Candida family, Candida albicans (ATCC 24433), and antibacterial activity against two strains: Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922) were confirmed in vitro. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
107.
Pilar Posadas Alberto Fernández‐Torres Celia Chamorro Irene Mora‐Barrantes Andrés Rodríguez Luis González Juan L Valentín 《Polymer International》2013,62(6):909-918
A step forward in the understanding of rubber vulcanization with organic peroxides is provided by combining a proper arrangement between polymer, vulcanizing agent and cure conditions. For this purpose, an ethylene–vinyl acetate copolymer with a high content of vinyl acetate (70 mol%) was used since a fully saturated polymer backbone allows its vulcanization via peroxide. For the range of conditions analysed here, it is shown that the predominant process taking place is crosslinking via radical recombination, minimizing or even avoiding undesirable secondary reactions such us polymer degradation. Once conditions had been optimized, peroxide vulcanization was analysed in more depth in the presence of 2,2,6,6‐tetramethylpiperidinyloxyl, which is a mediating stable free radical commonly used in controlled radical polymerization. Consequently, it was possible to differentiate the termination reaction from the initiation and propagation steps, allowing the determination of the enthalpy of formed C–C crosslinks as measured using calorimetry. It was possible to isolate and determine the contribution of the crosslinking pathway from the global vulcanization reaction by means of calorimetric methods at optimum conditions. In fact, this simple methodology could be an important tool for understanding in detail the complex peroxide vulcanization of elastomers since reactions involved in this process determine the final network structure, and thus the final elastic properties of these compounds. 相似文献
108.
Glycerol, an increasingly abundant by‐product of biodiesel production, is selectively converted to ketomalonic acid in one pot at pH 10 using NaOCl as regenerating oxidant in water at 2 °C in the presence of catalytic Br− along with the radical TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl). The reaction can also be conducted at completion over a sol‐gel silica glass doped with the nitroxyl radical. Considering the stability and versatility of such doped glasses, these materials show real promise as reusable metal‐free catalysts for the conversion of a readily available and renewable biofeedstock into a highly valued compound. 相似文献
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MariaLuisa Testa Rosaria Ciriminna Chakib Hajji Elena ZaballosGarcia Marco Ciclosi Jose SepulvedaArques Mario Pagliaro 《Advanced Synthesis \u0026amp; Catalysis》2004,346(6):655-660
The conversion of amino diols to aminohydroxy acids by oxidation of the primary hydroxy group mediated by homogeneous and heterogeneous TEMPO (2,2,6,6‐tetramethylpiperidine 1‐oxyl radical) is reported. The synthesis uses NaOCl as primary oxidant and TEMPO, either dissolved in the homogeneous phase or entrapped in a sol‐gel matrix, as catalytic mediator. Homogeneous TEMPO is suitable for the oxidation of aliphatic methylamino diols, while the hybrid organic‐inorganic silica sol‐gel catalysts are more selective mediators for the oxidation of benzylic amino diols like the potent antibiotic chloramphenicol which, under homogeneous conditions, are unselectively oxidized to benzoic acids. 相似文献