高中化学教学中合作学习的有效性研究

探索保证合作学习有效性的策略是提高其实践性、实效性的需要。观察高中实验区的化学课堂教学,教师在组织学生合作学习时存在合作学习任务设计不当、小组成员分工不明、合作要求不清、指导不力、合作时间不足、组织方法单一、交流随意、评价不全等问题。研究合作学习的内容特点;小组的规模、构成、角色分工;实施时内容的安排,组织的方法;根据任务确定合作学习时间;对学生合作技能进行指导;评价关注三维目标、让学生明确评价标准等,都是组织有效合作学习的策略要点。     

新课程实施中对小组合作学习的再认识

通过调查研究和实践,对小组合作学习中小组产生的办法和过程、组建小组的约定、合作活动的加强、学习的评价方式、合作活动的控制产生了新的认识。     

基于小组合作学习的“线上预习–翻转课堂–课后探究”教学模式在化工原理教学中的应用

在化工原理国家一流线上课程与线上线下混合式教学基础上,开展了基于小组合作学习的线上预习–翻转课堂–课后探究的教学探索。以化工原理精馏单元操作中的塔板数简捷计算为例,对该教学模式进行阐述。通过班级分组、布置课前思考题,引导学生带着问题开展线上预习与小组合作学习,充分发挥了学生学习的主动性,大幅提高了线上预习、线下翻转课堂的教学效果与效率。通过师生翻转课堂教学与小组合作学习,使学生掌握了解决复杂工程问题的思路与方法,培养了学生解决复杂工程问题的能力。通过课后延伸问题与小组合作,引导学生课后进行学习与探究,学生建立了比现有文献适用范围宽得多的塔板数计算方程,培养了科学研究与创新能力。化工原理教学实践表明,基于小组合作学习的“线上预习–翻转课堂–课后探究”是一种较高效、通用性较强的高等工程教育教学模式。     

基于师生主导平衡的有机化学教学实践

有机化学课程的教学实践以培养学生学习和思考能力为核心目标,展开多种形式的教学活动。在教师所营造的利于学习的氛围下,课前学生撰写课程论文,展开自己的发现学习之旅;课堂小组导学、学生变构、教师关联;课后调用巩固,构建个性化的知识网络。教学改革实现课内和课外学习相结合,自主探究、合作学习、教师讲授有机结合,调动学生的主动性、创造性以及合作交往的社会性,学生的整体素质得到有效提高。     

基于学生自主选题形式的教学实践与思考

在实践的过程中逐步积累并形成的学生与学生之间的互问、互查和互测的教学方法,使学生在自主选题、小组合作和参与评价的过程中,以多种形式优化学生学习过程中知识结构的形成,引导学生主动反思,改变以往被动接受、被动练习的学习状态,提高学习的主动性,促进教学方法和学习方式的改变。     

小组学习在日常化学教学中有效实施的策略

小组学习是培养学生合作能力和团队精神的重要途径。本文总结了在日常化学教学中组织学生进行小组学习的经验,提出有效实现小组学习的策略是设计主动建构型任务和改变评价方式。并以两个化学教学实例说明了主动建构型任务的特点以及实施的效果,设计了将个人评价和小组评价进行对立统一的定量组合的评价方式。     

研究性学习在精细化工课程教学中的实践与探索

在精细化工课程中以食品添加剂与食品安全问题为专题开展了研究性学习。以学生兴趣为导向,采用主题离散式的选题方法,开展小组合作研究。重视学习过程和学习能力培养,采用多种方式相结合的方法进行评价,并对研究性学习在实施过程中存在的问题进行了探讨。实践表明,研究性学习可有效地激发学生的学习兴趣,培养学生的探究能力和综合素质。     

研究性学习中学生的体验

本文通过实践、调查、反馈,对研究性学习中学生的态度,学生对研究性学习中小组、选题、老师的要求,研究性学习的意义、基本特征,在研究性学习进行的过程中需要处理好的选题、建组、管理、评价以及与必修课的关系等问题,提出了一个比较清晰的认识。     

化学课堂采用小组合作学习方式的实践与思考

随着课程改革的深入,在化学教学中我们越来越关注学生在学习过程中的情感体验,重视学生之间和师生之间的交流与合作。小组合作学习是实现上述目标较为有效的学习方式。就化学课堂中采用小组合作学习方式的具体教学设计思路、实施关键及反思等几个方面进行了阐述。     

化学合作学习的教学设计研究

合作学习以组内异质、组间同质为合作学习小组的基本组织形式,系统利用教学中诸动态因素之间的互动,促进学生的学习,以计个人和团体成绩为评价标准,从而共同完成教学的目标.本文结合合作学习的内涵和理论研讨了合作学习的意义,并提出了中学化学教学中的5种化学合作学习方式.     

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.     

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.