共查询到20条相似文献,搜索用时 62 毫秒
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Hiroaki Koga Kohei Sakata Yoshinori Ato Akihide Hayashi Kohei Tada Mitsutaka Okumura 《催化学报》2016,(10):1588-1593
平均粒径为2–10 nm的聚合物稳定的Au纳米簇(NCs)表现出独特的催化性能。多个研究表明,影响聚合物稳定的Au NCs催化活性的主要因素为: Au NC尺寸的控制、聚合物的选择以及反应条件的优化。这是由于聚合物稳定的Au NCs在多个催化反应中表现出明显的尺寸效应,其催化活性也因所采用的聚合物和反应条件的不同而不同。为了阐明影响聚合物稳定的Au NCs催化活性的内在原因,众多研究者关注于聚合物稳定的Au NCs催化中的理论计算与实验的相互影响。本文主要总结了聚合物稳定的Au NCs中这种相互影响的研究进展。 相似文献
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本文审视、反思了学生学习化学知识的目的和过程,着重指出:学生深入学习化学知识的困难在于知识的网络化水平和可具体化水平较低。如果学生未能较好地掌握知识结构,即基础知识的合理组合,就无法形成合理的认知结构,也很容易造成学生负担过重,直接影响智力的发展、能力的培养和学习积极性的提高。为了实现教师的"教"向学生的"学"顺利转化,并逐步实现学生从"学会"达到"会学"、"乐学"的境界,提出了化学知识的可具体化问题;讨论了怎样的化学知识才是可具体化的知识,提高化学知识的可具体化水平有哪些方法和原则,特别是知识的纵向联系和知识的横向联系在化学教学实践中有何作用,如何运用。这对化学教学中进一步突出知识结构,形成合理的认知结构,并实现二者的统一有很大的促进作用。 相似文献
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煤中砷的测定方法及其赋存形态的研究进展 总被引:1,自引:0,他引:1
对近10年中国内外煤中砷量的测定方法以及煤中砷的赋存形态方面的研究进展作了综述。内容涉及测定煤中砷时试样的前处理方法,砷的各种测定方法和煤中砷的赋存形态研究以及各种形态砷的提取方法。对上述有关问题的发展前景也提出了期望(引述文献35篇)。 相似文献
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硝酸和铜反应的演示实验和学生实验的常规做法都会逸出大量的一氧化氮和二氧化氮,严重影响师生的身体健康,为此,我们对该实验进行了如下改进:1实验装置及药品将干燥管下端接一直导管插入锥形瓶中组装成如图所示的装置。2操作步骤和现象(1)浓硝酸和铜反应向锥形瓶中加入约15mL浓硝酸,打开止水夹A、B,用洗耳球将酸液压入干燥管内至浸没铜片,随即关闭A。反应迅速进行,干燥管内产生大量红棕色气体,液体同时变蓝。实验完成后,从碱液中取出导管,打开A,使液体流回锥形瓶,反应停止。关闭A、B,避免二氧化氮逸出。(2)… 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
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A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions. 相似文献