共查询到20条相似文献,搜索用时 140 毫秒
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前文报道了各种甲氧基萘用三甲硅基氯磺酸酯在非极性溶剂中进行的磺化反应。本文研究了四种卤代苯和六种卤代萘用三氧化硫在非极性溶剂中进行的磺化反应。卤代芳香化合物用氯磺酸,浓硫酸及发烟硫酸进行的磺化反应已有报道。在芳香化合物的亲电取代反应中,卤素的定位效应取决于以下两个因素。首先,负的诱导效应体现为F>Cl>Br>I,且对邻位的影响远大于对位的影响。而正的共轭效应亦体现为F>Cl>Br>I,对对位的影响最大。单取代卤苯在浓硫酸中进行磺化反应,几乎专一地发生在4—位上。说明尽管卤素降低了芳香环上的电子云密度,但仍为邻对位定位基。三氧化硫(SO_3)是最剧烈的磺化剂,溶于非极性溶剂二氯甲烷中,既减少了付反应,又可在室温下进行高效率的磺化反应。 相似文献
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本文研究 了在非极性溶剂二氯甲烷中卤代苯和卤代萘用SO~3进行的磺化反应. 卤代苯最初开始磺化反应的产物是4-磺酸, 2-卤代萘的产物是8-磺酸. 当用过量的SO~3长时间反应时, 磺化反应得到三取代产物. 相似文献
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卤代萘与三氧化硫的磺化反应林静,邹友思(厦门大学化学系,厦门,361005)关键词磺化反应,三氧化硫,卤代萘甲基和甲氧基萘用三氧化硫进行的磺化反应已有报道[1~3],而卤代萘的磺化反应迄今未见报道.本文研究了6种卤代茶在非极性溶剂二氯甲烷中用三氧化硫... 相似文献
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基于卤代烷亲核取代(SN2,本文记作SN2C)反应,介绍关于卤代烷亲卤取代反应(SN2X)的理论基础、影响因素;还介绍了几类常见亲核试剂参与的SN2X反应以及关于不对称催化SN2X反应的最新研究进展。本文内容是对现行教科书相关内容的深度延伸和补充。 相似文献
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二卤卡宾与羰基化合物反应的研究进展 总被引:6,自引:1,他引:6
对近年来二卤卡宾与羰基化合物的反应机理研究进行了总结,指出二卤羰基Yilde为反应的中间体,并对影响二卤羰基Ylide的稳定性及后续反应的因素如底物的立体效应,取代基的电子效应,Captodative效应以卤原子半径大小进行了讨论。 相似文献
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5,10-CH+-THF向邻苯二胺转移一碳单元反应的理论研究 总被引:2,自引:0,他引:2
叶酸辅酶在酶催化的一碳单元转移过程中具有重要的作用,已有大量的实验及实验模拟对其生物学功能进行了研究分析.本文用PM3半经验方法对5,10-CH+-THF向邻苯二胺转移一碳单元的反应进行了理论研究.结果表明,5,10-CH+-THF中的咪唑啉环有两种开环方式,从而使得该反应可以通过两种途径实现,每一种途径都经历了6个反应步骤,其中包括限制速度的两次质子转移步骤.优化计算了每个步骤所有可能的中间体和过渡态的结构和能量,并通过比较分析得到了各反应阶段的最优中间体和过渡态结构. 相似文献
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酶催化的一碳单元转移反应在生物合成和代谢过程中具有重要的作用 ,并与抗癌药物设计和合成密切相关 .虽然催化不同一碳单元转移反应的酶不同 ,但大多数酶需要四氢叶酸作辅酶 .四氢叶酸辅酶传递一碳单元的化学与其N5,N1 0的ΔpKa 密切相关 ,而与嘧啶环及谷氨酸残基部分无关 ,后两部分的作用是把辅酶结合在适当的酶蛋白表面上[1 ] .当可转移的碳处于甲酸态时 ,四氢叶酸辅酶以衍生物 5,1 0 CH+ THF(1 )的形式存在 ,其中可转移的碳与N5,N1 0相连形成五元环 ,是反应的活性中心 .由于酶反应体系的复杂性 ,在实验和理论研究中大多建… 相似文献
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Milivoj Lovric 《Russian Journal of Electrochemistry》2016,52(10):938-942
A reversible electrode reaction that is followed by totally irreversible chemical reaction is investigated theoretically. The influence of chemical reaction on two components of the net response of differential pulse polarogram is analyzed. It is demonstrated that this EC mechanism depends on two kinetic parameters and that their critical values can be used for the measurement of the rate constant of chemical reaction. 相似文献
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本文根据热动力学的理论和方法,建立了二种可逆反应动力学的数学模型和研究方法,并通过氨与硝基乙烷的2-2型和准1-1型可逆反应的热动力学加以验证。 相似文献
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Qi Chuan‐Song Feng Da‐Cheng Kang Cong‐Min Cai Zheng‐Ting 《International journal of quantum chemistry》2003,92(5):451-456
Quantum mechanics is used in this article to study one‐carbon unit's transfer from 1,10‐tetrahydroquinoxaline analog to methylamine. The computation result shows this reaction can be completed via two paths. Each path experiences two processes of proton transferring and bond rupturing. The structures and energies of all possible stationary points have been calculated by different methods. By analyzing the result, we can find that along the reaction route the proton transfer reaction has the highest energy barrier, which indicates that a general‐acid catalysis exists in this reaction. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 相似文献
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There are two different views on the definition of reaction molecularity in physical chemistry textbooks and related literatures so far. We give a deep discussion about this conception herein. Starting with the development of chemical kinetics and the definition of elementary reaction and state-state reaction, we clarify that elementary reaction and state-state reaction are the conceptions belonging to macro-and micro-systems, respectively, and reaction molecularity is also belonging to micro-conception. Based on this conclusion, we think that the more reasonable definition of reaction molecularity should be "the number of chemical particles that take part in a state-state reaction (or an elementary chemi-physical reaction) as a reactant". 相似文献
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Mechanistic Investigation on Rhodium(Ⅲ)-Catalyzed Cycloaddition of 2-Vinylphenol Derivatives with Ethyne or Carbon Monoxide by DFT Study 下载免费PDF全文
Rhodium-catalyzed cycloaddition reaction was calculated by density functional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives. In this work, we conducted a computational study of two competitive mechanisms in which the carbon atom of acetylene or carbon monoxide attacked and inserted from two different directions of the six-membered ring reactant to clarify the principle characteristics of this transformation. The calculation results reveal that: (ⅰ) the insertion process of alkyne or carbon monoxide is the key step of the reaction; (ⅱ) for the (5+2) cycloaddition reaction of acetylene, higher energy is required to break the Rh-O bond of the reactant, and the reaction tends to complete the insertion from the side of the Rh-C bond; (ⅲ) for the (5+1) cycloaddition of carbon monoxide, both reaction paths have lower activation free energy, and the two will generate a competition mechanism 相似文献
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In this paper, it is clearly demonstrated that the dependence of the rate of evolving heat on time is completely described
by using Mangelsdorf's method in terms of three processes with excellent precision. The first two exothermic processes take
into account the fact, that the reaction occurs by two competitive mechanisms: one is a non-catalytic mechanism and the other
is catalyzed by OH-groups formed during the reaction. The third one refers to the endothermic process where the reaction is
accompanied by diffusion of the reaction products. The distinctive feature of this diffusion process is that it is the coupling
of the reaction kinetics and rearrangement of the chains built to the rigid supramolecular structure. This simple model allows
accurate simulation of kinetic behaviour.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献