以无机化学习题为例探讨电极电势的应用*

电极电势是氧化还原反应中重要的物理量,其概念的理解和运算是教学重点和难点,在无机化学习题的基础上,将电极电势和四大平衡相结合,通过一题多解开拓学生的思维,旨在帮助学生巩固所学知识,加以灵活运用,做到举一反三、触类旁通,提高学习效率及科学思维能力,加深对化学基本原理的理解和掌握。     

数轴在电化学教学中的妙用

电池符号、电极电势和电极极化是物理化学电化学教学中三个非常重要的知识点。本文以极易记忆的“数轴”为模型,阐述了数轴在这三个方面教学中的妙用。基于实例详细说明了如何以数轴模型理解记忆电池符号的规定、电极电势的大小及应用和电极极化的概念及应用。     

关于标准氢电极

在电化学教学、生产和科学研究中,电极电势是一个基本的和重要的概念。电极电势的测定在电极过程动力学、腐蚀和电势—pH图等方面都有着广泛的应用。因此,早已有文章就电极电势的有关问题进行过讨论。对于电极电势,一些物理化学教科书中大都是采用国际纯粹与应用化学联合会(IU-     

深入原电池原理本质促进学生观念和能力的发展

在调查分析高三学生对原电池原理的理解及应用状况的基础上,论述了从电极电势及平衡移动的角度理解原电池中产生持续电流的原因,有助于学生能量观的建构及学生能力的发展。以高三原电池复习教学为例,阐述了促进学生理解学科知识本质的探究活动的设计。     

金属元素学习中的两个问题

金属元素是化学元素的重要组成部分。学员在学习中对金属活泼性与电极电势和电离能的关系、金属不同价态的稳定性及其相互转化的条件等,常有一些模糊的认识,本文拟就这两个问题进行一些讨论。一、金属活泼性与电极电势和电离能的关系金属的电离能和电极电势是两个不同的概念,虽然二者都能用来衡量金属活泼性（失电子能力）的大小,但是应用的条件是不同的。     

揭示内在规律 培养学生能力——对元素化学教学的探索

本文在归纳周期系中元素氧化态递变规律及运用电极电势、电势图阐明无机反应规律等方面作了一些探索,以在无机化学教学中使学生在学习元素化学性质的同时培养理解、分析归纳的能力。     

相对电极电势与“绝对”电极电势简论

本文从电池电动势的组成出发,讨论了相间电势、单电极电势及氢标电极电势的区别;并分别从电子能量的构成及电极反应的自由能变考虑,介绍了三种“绝对”电极电势的概念及相互关系,从而对物化教学及无机教材中的有关问题提出点滴浅见,以资讨论。     

无机化学中的一题多解

无机化学计算中采取一题多解可开拓学生的思维,加深对化学基本原理的理解和掌握,有利于巩固和提高所学知识,并加以灵活运用,做到触类旁通。文章以无机化学教学中化学平衡、电极电势2类问题的计算给予说明。     

AgCl/Ag标准电极电势的教学难点突破

对于有难溶物参与的电极反应,其标准电极电势的计算是教学中的一个难点。根据大一学生认知特点,通过转换视角,复习前期知识点,顺利实现计算AgCl/Ag电对标准电极电势的难点突破。     

中学生对“溶液”概念理解的可视化表征及启示

学生概念理解的可视化表征可以通过学生的作图来展示,分析图示可以获取学生概念理解的更加深入的信息。梳理了国内外有关中学生对“溶液”概念理解的研究,集中对学生的作图进行分析,呈现了中学生对“溶液”概念理解的可视化表征。针对作图发现的学生概念理解的结果,提出了促进中学生“溶液”概念理解的教学启示。     

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.