基于三重表征的大学有机化学教学策略

从宏观、微观和符号三种表征水平上认识和理解有机化学知识,并建立三者之间的内在联系,进而培养学生“宏观?微观?符号”三重表征思维方式,这对于有效地学习有机化学具有重要的促进作用。结合教学实践,探析了基于三重表征的大学有机化学教学策略。     

朝鲜族高中生化学三重表征转换能力的调查研究

利用多维分析系统（MAS）,采用2段式问卷并结合课堂观察,以普通高中物质结构与性质模块为内容,调查了延边地区朝鲜族高中生化学三重表征转换能力及其影响因素。结果表明：朝鲜族高中生化学三重表征转换能力由高到低依次为宏观-微观相互转换能力 、宏观-符号相互转换能力、微观-符号相互转换能力。     

九年级学生三重表征转换能力的发展过程:基于眼动的证据*

九年级学生在化学学习的过程中开始建立三重表征思维,同时,不同学业水平学生的三重表征转换能力会出现分化。为了探究学生在各个阶段三重表征转换能力的发展特点,采用眼动分析法对12名九年级学生进行了一学期的追踪实验。研究发现:(1)入门时期,学生进行不同表征之间转换的能力是有差异的,并且表现出转换和逆向转换能力的不对称性特点。学优生与学中生、学困生的三重表征转换能力有明显差异,但学中生与学困生的三重表征转换能力还没有表现出明显差异。(2)突破时期,学生进行宏观(中心)、符号(中心)、微观(中心)转换的注视点个数、测试总时间没有表现出统计学差异。学优生与学中生的转换能力分化更明显,学中生与学困生开始出现差异。(3)深化时期,学生宏观(中心)表征能力最强,符号(中心)表征能力次之,微观(中心)表征能力最弱。学优生与学中生、学困生的转换能力差异显著,学中生的间接转换频率明显增加。     

化学学习中"宏观-微观-符号"三重表征的研究

“宏观-微观-符号”三重表征是体现化学学科特征的思维方式,能增进学生对化学知识的理解。本研究在对三重表征思维方式进行分析的基础上,采用问卷调查的方法,对不同群体学生化学学习三重表征水平进行了探查和分析,为化学教学提供了一个新的视角。     

计算机模型应用于化学教学的若干策略

学生难以建立宏观-微观-符号三重表征及其它们之间的相互联系,造成大量的化学错误概念及学习障碍。为解决这一问题,国外学者广泛运用计算机模型于化学教学中,并取得良好效果,但国内相关研究相对滞后。论文在实证研究基础上,提炼出计算机模型应用于中学化学的若干教学策略,并结合具体教学案例加以阐述。这些策略包括：（1）创设问题情境,启发学生思维;（2）呈现宏微现象,理解科学知识;（3）训练科学方法,提高探究能力;（4）引导反思质疑,理解模型本质;（5）自主建构模型,增强建模技能。论文最后提出几条教学建议。     

基于建构化学基本观念的对比教学法——以“质量守恒定律”教学设计为例

在质量守恒定律的教学中,将对比教学法巧妙地运用于史料知识、实验探究、数据分析中,有助于实现学生宏观表征从"质"到"量"的突破,微观表征从"静"到"变"的转化,符号表征从"孤立"到"联系"的完善,从而建立宏观-微观-符号表征之间的联系,学生对定律的认识在从模糊到清晰并臻于科学的过程中,构建物质变化观。     

高中化学教科书中类比特征的分析及编写建议

高中化学教科书中类比的分析表明：（1）类比数目较少;（2）目标物以微观结构和抽象概念为主,类比物主要是学生熟悉的社会生活经验,学科知识较少;（3）类比呈现方式以文字描述为主,少数辅助于图像类比;（4）类比物与目标物之间的相似属性以结构关系为主,兼具结构与功能关系的类比不足;（5）类比相似属性的映射程度较高,但类比的局限性被忽略。建议教科书中类比的编写：适当增加类比的数目;扩展类比物的范围;重视宏观、微观和符号三重表征的类比设计;适时增编类比方法的指导。     

三重表征视域下的化学学习研究考查

梳理了三重表征研究范式下部分化学学习研究成果。基于三重表征,研究者细致考查学生在宏观表征、微观表征和符号表征等单维度化学学习中遇到的困难;结合信息加工模型,解释了化学学习机制,形成对化学学习的动态认识,指出以上研究中尚待完善之处,以期为化学学习的深入研究提供借鉴。     

利用手持技术探究铝的化合物之间的相互转化过程

高中铝的化合物（“铝三角”）之间的相互转化过程是高考高频考点,其中共涉及7个反应方程式,但学生对此大多停留在机械记忆层面上,认知思路和角度较混乱。从一道高考题出发,引入数字化手持技术设计4个滴定实验,利用电导率、pH传感器测得电导率、pH随时间变化的曲线,结合宏观、微观、符号和曲线表征多角度进行分析。利用四重表征分析方法,突破“铝三角”转化中双水解反应的认知难点,完善相关教学并提供参考建议,丰富手持技术在教学上的案例。     

提升三重表征融合能力的教学策略研究——以高中化学“电解质的电离”教学为例

结合高中化学"电解质的电离"中丰富的教学活动,以感知体验化、微观可视化、知识本源化、认识观念化和符号意义化为教学策略,丰富和深化宏观表征和微观表征,实现化学三重表征的高度融合。     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

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.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.