改革教学方法,提高扫描电镜实验教学效果

针对目前本科生扫描电镜实验教学中存在以理论讲解和教师操作为主,学生主动参与性差,教学效果不理想等情况,建立以提高实验教学效果为目标的教学改革方法。通过精心设计实验教学内容、改进教学方法,以实例教学法加深学生对二次电子和背散射电子像、分辨率及景深等抽象概念的理解,增加学生自制样品观察,突出能谱测试的应用场合。授课方式既有理论讲解,又有实例图示及相关计算,使实验教学更具趣味性,激发学生的求知欲望,体现学生的主体作用,培养学生分析问题、解决问题的能力,切实提高材料专业扫描电镜实验的教学效果。     

思维导图在仪器分析实验教学中的应用——以电化学分析实验为例

在电化学分析实验教学中引入思维导图,探讨了思维导图在仪器分析实验教学中的应用方法及效果评价。实验原理的教学依托“比较与对比图”和“逻辑思维图”,强调相关方法原理之间的联系,突出新方法的特点;实验步骤则以清晰易懂的“流程图”方式呈现。教学实践表明,思维导图有利于学生对实验基本原理的理解和掌握,提高了学生的实验兴趣,促进了学生的独立思考能力和解决问题的能力,显著提升了实验教学效果。     

化学实验教学中的测量不确定度

在化学实验教学实践中由于误差分析的角度和方法不同,显著影响了实验数据和结果的表达和比较.实验结果和误差分析采用测量不确定度表达方式,可克服传统误差理论的弊端,有效提高实验数据分析效率.通过介绍大学化学实验教学中测量不确定度的由来、意义和评定要领,完成一个评定实例,以期扩展测量不确定度评定方法在化学实验教学中的应用范围,推动新知识在化学实验教学中的普及.     

仪器分析课程教学模式新探

针对仪器分析课程的特点,将"教研结合"的教学模式用于仪器分析理论教学中。通过对科研实例的深入解析,将涉及的相关教材知识穿插讲解。同时在仪器分析实验教学中采用"翻转课堂"的教学模式,即以"学生讲为主、教师讲为辅"的方式改变传统实验教学的弊端。从理论与实验两方面对仪器分析课程教学模式进行改革。     

物理化学教学中理论与实验相互渗透的方法探究

针对物理化学课程的特点和教学中存在的一些问题,结合实例探讨了理论与实验相互渗透的教学模式在物理化学教学中的应用。实践证明在理论教学中设计实验和在实验教学中强调理论分析的做法可以有效地提高学生的学习兴趣和参与教学的积极性,从而取得较好的教学效果。     

高分子材料的专业实验课程体系改革的探讨

在专业实验教学中,为有效提高学生实际动手能力、分析和解决问题能力,我们改变了传统专业实验教学体系。首先,在新的专业实验教学中开设综合性、设计性实验,在实验中鼓励学生阅读、分析、整理文献,并在此基础上体会如何制订合理的实验方案;其次,制定新的实验考核方案,以便于提高学生的自主创新能力及实践综合素质。     

结合理论课堂的知识点设计高分子材料合成实验课程

尝试在"高分子材料合成创新实验"课程中将理论课的知识点巧妙地融入到实验教学中，有目的地设置实验环节，通过对实验现象的分析，帮助学生巩固理论课知识点。为了充分利用实验的等待时间，在有目的地组织学生对实验进行预习的基础上，还尝试"激励学生参与"实验课的教学，鼓励学生以实验小组的形式讲解与实验相关联的理论知识，进一步巩固相关知识点，并扩充知识面。2年的实验教学反馈表明，这些尝试既有效巩固了理论课堂的知识点，做到了活学活用，又激发了学生的学习兴趣，提高了分析问题的能力。     

数字比色分析法在大学本科化学实验中的应用*——铁-磺基水杨酸配合物稳定常数的测定

数字比色法是近年来发展起来的一种检测方法。“铁-磺基水杨酸配合物稳定常数的测定”是大学无机化学中的经典本科学生实验。将数字比色法应用于该学生实验并与常规的分光光度法分析结果进行了对比。首先,探究了数字比色法的数据采集,即照片拍摄条件的因素控制。其次,通过数据比较分析了数字比色法的应用特点。结果显示,数字比色法的灵敏度介于目视比色法与分光光度法之间。该方法对较小的颜色差异分辨能力不足而对比较明显的颜色变化区分能力较好。在本科实验教学中,将该方法应用于颜色变化梯度明显的化学反应体系可获得较好的分析结果。     

“产、学、研、用”一体化仪器分析实验教学改革的探索与实践

仪器分析实验在大学化学实验教学中占有非常重要的地位,结合吉林大学化学学院仪器分析实验“产、学、研、用”一体化教学模式,从实验教学内容的改革与探索和实验教学平台的建设与实践2个方面,围绕教学仪器的研制与开发、教学方法与课程设计、育人模式与运行机制等内容进行了分析和论述。     

定性分析实验教学体系改革的探索与实践

提出的“定性分析实验教学体系”既保持了传统硫化氢系统分析的基本框架和教育功能,又简化了实验步骤,提高了分析效率,降低了实验成本。通过加强未知液和分析方案设计等研究性实验的教学,以及组织环保兴趣小组等活动,有力地促进了学生实验操作技能、理论水平和应用能力的提高。其核心内容“25种阳离子定性分析实验教学方案”在本、专科化学教学中,都是值得推广的。     

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.