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在金属离子参与下S(Ⅳ)的催化氧化反应是大气含水体系中S(Ⅳ)转化为S(Ⅵ)的重要反应.普遍认为大气中的主要金属元素 Mn,Fe,Cu和 Co对 S(Ⅳ)的氧化有催化作用.尽管 Mn(Ⅰ)和 Fe(Ⅱ)对于 S(Ⅳ)催化氧化的化学动力学已被广泛研究,但至今尚未取得一致的结果;有关Mn(Ⅰ)和 Fe(Ⅱ)催化氧化的协同作用亦是人们争论的问题。本工作在分别研究了Mn(Ⅰ)和 Fe(Ⅱ)对 S(Ⅳ)氧化的催化作用的基础上,进一步考察了 Mn(Ⅰ)和 Fe(Ⅱ)是否存在着协同催化作用.另外,还探讨了Fe(Ⅱ)和活性炭、Mn(Ⅰ)和活性炭对S(Ⅳ)的氧化是否存在着协同催化作用. 相似文献
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研究了相转移催化剂(Bu4NHSO4)作用下,Cr(Ⅵ)/Cr(Ⅲ)间接氧化还原体系电氧化苄基醚。实验结果表明,苄基醚可选择性地高产率氧化为苯甲醛,阳极液中Cr(Ⅲ)可以循环使用。 相似文献
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吴诚 《理化检验(化学分册)》1999,(6)
问:1.Mn(Ⅱ)的过硫酸铵氧化光度测定法为什么至今仍被广泛应用于金属材料中锰的测定? 2.过硫酸铵氧化Mn(Ⅱ)至Mn(Ⅲ)反应的酸度要求如何?反应宜在何种酸的介质中进行? 3.氧化Mn(Ⅱ)至Mn(Ⅶ)应加入多少过硫酸铵? 相似文献
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分别以离子液体[Hex-mim]BF4, [Bmim]BF4, [Bmim]PF6和[Omim]BF4为溶剂, Co(Ⅱ), Mn(Ⅱ)或Ni(Ⅱ)/NHPI(AIBN)为复合催化剂, 考察了不同离子液体-催化剂体系中常压分子氧氧化芳烃侧链烷基的反应. 在[Hex-mim]BF4中, Co(Ⅱ)或Mn(Ⅱ)/NHPI可有效地催化芳烃侧链烷基的分子氧氧化. 在优化条件下, 乙苯、正丙苯和正丁苯分别以高达90%, 94%和93%的收率得到相应的芳香酮; 甲苯和对位取代甲苯以32%~47%的收率被氧化为相应的芳香酸. 离子液体及金属催化剂体系在减压下除水后, 可循环使用. 相似文献
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催化动力学光度法测定痕量锰 总被引:1,自引:0,他引:1
在H2SO4介质中,在表面活性剂壬基酚聚氧乙烯(7)醚的活化下,Mn(Ⅱ)催化溴酸钾氧化甲基紫褪色,建立了动力学光度法测定痕量Mn(Ⅱ)的新方法.考查了最佳试验条件并进行了动力学参数的测定;该方法检出限为2.3×10-7 g/L;线性范围0.0002~0.014 μg/mL;最大相对标准偏差为4.8%.用于水和面粉的测定,回收率在95.0%~104.7%之间;对面粉样用石墨炉原子吸收法进行了对比试验,方法相对误差低于±5.0%. 相似文献
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相转移催化下Mn(Ⅲ)/Mn(Ⅱ)体系对醇类的选择性电氧化 总被引:2,自引:0,他引:2
以Mn(Ⅲ)/Mn(Ⅱ)为间接氧化还原体系,用间接电氧化的方法,在相转移催化条件下对醇类的氧化进行了研究。结果表明,在所用实验条件下,Mn(Ⅲ)可以方便地在电极上生成及再生,对苄醇类及二级脂肪醇类能高产率地选择性氧化成相应的羰基化合物。 相似文献
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G. V. M. Sharma B. Lavanya A. K. Mahalingam Palakodety Radha Krishna 《Tetrahedron letters》2000,41(52):10323-10326
Mn(OAc)3 has been successfully developed as a new oxidant for the regeneration of DDQ from HDDQ. This DDQ regeneration technique, making use of 3 equiv. of Mn(OAc)3–DDQ (10 mol%), was applied to the deprotection of p-methoxy benzyl (PMB) ethers. 相似文献
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Ramesh Naik 《合成通讯》2013,43(10):1723-1726
Dimethylsulfoxide (DMSO) oxidizes benzyl ethers into corresponding benzaldehydes at 110°C; the reaction is accelerated by 49% aq. HBr. The conditions work well for different aryl‐substituted benzyl ethers. This protocol is inert toward dialkyl ethers. 相似文献
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Sodium hypophosphite plus palladium-charcoal is a mild, economical, selective system for the reduction of carbon-carbon double bonds and hydrogenolysis of benzyl ethers and benzyl carbonates. 相似文献
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Chemoselective and Direct Functionalization of Methyl Benzyl Ethers and Unsymmetrical Dibenzyl Ethers by Using Iron Trichloride 下载免费PDF全文
Dr. Yoshinari Sawama Ryota Goto Saori Nagata Yuko Shishido Dr. Yasunari Monguchi Prof. Dr. Hironao Sajiki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2631-2636
Methyl and benzyl ethers are widely utilized as protected alcohols due to their chemical stability, such as the low reactivity of the methoxy and benzyloxy groups as leaving groups under nucleophilic conditions. We have established the direct azidation of chemically stable methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols. The present azidation chemoselectively proceeds at the secondary or tertiary benzylic positions of methyl benzyl ethers or unsymmetrical dibenzyl ethers and is also applicable to direct allylation, alkynylation, and cyanation reactions, as well as the azidation. The present methodologies provide not only a novel chemoselectivity but also the advantage of shortened synthetic steps, due to the direct process without the deprotection of the methyl and benzyl ethers. 相似文献
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Subhasish Neogi 《合成通讯》2013,43(13):1901-1915
Palladium catalysed transfer hydrogenation using cyclohexene as the donor is found to deprotect readily alcohol benzyl ethers and aliphatic benzyl esters. The phenol benzyl ethers and benzyl benzoates are stable under these conditions. 相似文献
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А. R. Bayguzina L. I. Gimaletdinova R. I. Khusnutdinov 《Russian Journal of Organic Chemistry》2018,54(8):1148-1155
Synthesis of benzyl alkyl ethers was performed in high yields by intermolecular dehydration of benzyl and primary, secondary, tertiary alcohols under the effect of copper containing catalysts. The formation of benzyl alkyl ethers occurs with participation of benzyl cation. 相似文献
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Rare earth metal trifluoromethanesulfonates [rare earth metal triflate, RE(OTf)3] were found to be efficient catalyst for benzyl-etherification. In the presence of a catalytic amount of RE(OTf)3, condensation of benzyl alcohols and aliphatic alcohols proceeded smoothly to afford the benzyl ethers. The condensation between benzyl alcohols and thiols also proceeded, and thio ethers were obtained in good yield. In these reactions, RE(OTf)3 could be recovered easily after the reactions were completed and could be reused without loss of activity. 相似文献
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A direct Cross-Dehydrogenative-Coupling (CDC) between benzyl ethers and simple ketones was developed without using any metal catalyst. By using DDQ, various benzyl ethers and simples ketones were coupled together directly to form beta-alkoxyl ketones efficiently. A mechanism in which the DDQ serves the double roles of an oxidizing agent and an organomediator was proposed. 相似文献
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The mechanism of 1,2-aryl shifts in the Wittig rearrangement of α-metallated benzyl aryl ethers has been investigated by a detailed examination of the behavior of the following ethers: benzyl phenyl ether, benzyl para-tert-butyl- and meta-tert-butyl-phenyl ethers, benzyl 2-bromo-4-tert-butylphenyl ether and dibenzo[b,d] pyran. The failure to trap any aldehyde intermediate, the ease of rearrangement for the pyran, the lack of evidence for an aryne intermediate with the benzyl butyl ethers and other circumstantial evidence have led to the proposal of an intramolecular pathway in which radical pairs are generated and then collapse to the isomeric carbinolate. 相似文献