小型封闭式电解器的新设计

本文介绍一种小型封闭式电解器,它制作简单,使用方便。以电解饱和NaCl溶液为例,对电解器的制作和使用说明如下:1 电解器的制作 如图所示进行组装,要求是:     

低浓度NaCl溶液Ti/Pt阳极电解制备活性氯

以Ti板阴极、Ti/Pt阳极组成无隔膜电解装置,电解低浓度NaCl溶液制得活性氯.研究电解时间、电流密度、氯离子浓度、溶液pH值对活性氯浓度及电流效率的影响.结果表明:电解时间增加,活性氯浓度增加,而电流效率逐渐降低;初始阶段活性氯浓度增加较快,近1 h活性氯浓度趋于稳定;增加氯化钠浓度可提高活性氯浓度和改善电流效率;微酸性电解液有利于提高活性氯浓度.电解过程中,溶液电导率不断降低,pH值变化范围在1之内.     

电解生成亚铁离子返滴定法测定消毒液中过氧化氢含量的数字化实验*

氧化还原与电解的相关知识是中学化学学习的重点内容。应用自主研制的MXLab21先进数字化实验系统电解Fe₂(SO₄)₃溶液,用电解生成的Fe²⁺直接滴定KMnO₄溶液以测定其浓度,再用返滴法测定消毒液中H₂O₂的含量。对恒电流电解的最佳条件如Fe₂(SO₄)₃溶液浓度及电解电流大小进行了优化。该数字化实验系统相比较于常规数字化仪器(或手持技术)的优越性在于其自带电解、搅拌及控制系统,能在电解的同时利用电生物质实现对待测物质的准确测定,测定时间短(不超过4 min)。本实验采用预设终点电势值的方法自动估计滴定终点,不但便捷准确,且呈现出的实时直观的电势和电量随时间变化的动态曲线便于学生理解电解及氧化还原滴定反应的微观本质,对中学化学教学及化学学科核心素养的培养具有重要价值。     

电解质溶液电解的综合知识教学

不少学生能够理解电解的原理,但是把电解质水溶液电解时发生的溶液 pH 值的改变,析出物质量的比较、两极产物等联系在一起探讨则感到困难重重。因此在学过有关电解教材以后,可以引导学生进行以下总结,以突破这些难点。1. 整理思路寻求规律在学过典型电解质水溶液的电解过程和产物等知识以后,经分析比较有针对性地得到下述思路：     

磁场对NaCl溶液电解反应的影响

超导电磁船利用固定在船体上的超导磁铁在海水中形成强磁场,并在与此磁场相垂直的方向上通直流电电解海水。由于电磁相互作用,产生洛伦兹力,利用其反作用力,推动船前进。磁场对电解反应的影响,不仅与超导电磁船相关,而且是电化学领域中的一个基础研究课题。作者等在5T磁场下电解NaCl溶液时,观察到加磁场后Cl_2的发生量有减少的     

电解熔融氯化钠演示实验设计

电解熔融NaCl实验具有较高的教学价值,但由于实验要求太高在教学实践中难以实做。因此通过实验研究,指出电解熔融NaCl实验设计要解决产生高温、降低NaCl熔点、选择电极、选择容器、如何取出钠等问题,在此基础上设计电解熔融NaCl并检验金属Na和Cl2的演示实验,该实验易于操作,现象明显,能够为电解的教学提供有效支持。     

介绍一种研究电解质电离及离子性质的实验装置

在中学讲授电解质溶液导电及电解时,总要给学生讲解:电解质溶液之所以能够导电,是由于溶液里有能够自由移动的离子,通电后,在电场的作用下,这些自由移动的离子作定向移动,阴离子向阳极移动,阳离子向阴极移动。为了讲授这些知识,建议配合以下演示实验,这样学生就更容易理解和掌握。     

对Shil'nikov混沌特性拟合计算的改进

对H₂SO₄/NaCl溶液电解Cu体系中出现的Shilnikov混沌特性的拟合计算进行了改进,求出了体系的Lyapunov指数,确定出体系存在混沌吸引子,并且发现计算机模拟出的混沌吸引子的形状与实验得出的吸引子十分相似.     

基于数字化实验,落实 “证据推理与模型认知” 学科核心素养——以拓展探究复分解型离子反应发生条件的教学应用为例

本研究利用数字化电导率传感器对离子反应的发生条件实验进行拓展设计,测定常温下,等浓度的CH₃COONH₄溶液分别与蒸馏水、NaCl溶液、HCl、NaOH溶液混合后的电导率变化,以实验的数据和图像为证据,推理部分离子反应的实质和发生条件,促进学生对离子反应内涵的认知,在教学中渗透 “证据推理与模型认知”学科核心素养。本研究是对教材内容的补充和拓展, 为教师进行离子反应的教学实践拓展提供一定参考。     

疏水缔合水溶性聚合物AO的溶液粘度行为研究

研究了稀溶液中疏水链链长、无机电解质NaCl和CaCl2对疏水缔合水溶性丙烯酰胺／甲基丙烯酰氨乙基-二甲基烷基溴化铵／丙烯酸钠共聚物(AO)在水溶液中的特性粘数和Huggins常数的影响，以及聚合物AO-8的特性粘数和Huggins常数随温度的变化。结果表明：在稀溶液中，无机电解质离子强度增大，共聚物AO在NaCl和CaCl2溶液中的特性粘数减小，Huggins常数增大。在亚浓溶液范围对聚合物质量分数、温度、剪切速率及NaCl含量对聚合物的水溶液表现粘度的影响进行了研究，观察到疏水缔合聚合物盐水溶液在NaCl含量提高的情况下，出现的增粘现象。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

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.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

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.