2-甲基-2-己醇制备实验的改进与创新设计

用Grignard试剂制备2-甲基-2-己醇是大学有机化学实验课程中的一个经典实验.传统方法中,通常使用碘作为反应引发剂,使用10％ 硫酸溶液水解中间产物,这使得副反应较多,目标产物产率较低.本研究探究了反应加热顺序、引发剂种类和中间体水解条件等对产物产率的影响,试验结果表明:最优条件下,改变加热顺序,使用1,2-二溴...     

管式微反应器内测定乙二醇和乙酸酯化反应动力学实验

将连续化微通道反应技术引入化学工程与工艺专业实验课程中,以乙二醇和乙酸酯化生成乙二醇单乙酸酯和乙二醇二乙酸酯为反应体系,通过改变反应温度和停留时间探究测定反应动力学。该实验利用气相色谱对产物组分进行分析,利用MATLAB软件进行数据处理并模拟获得较优工艺条件。实验过程安全可靠,可操作性强,有利于提高学生综合运用知识的能力和严谨规范的科研能力。     

杨木快速裂解过程机理研究

将现代化学分析领域中重要的分析手段－裂解气相色谱法应用于对杨木 快速裂解过程机理的研究。通过系统考察裂解温度400－800℃、裂解挥发性产物停留时间0．6－4s。升温速率改变对杨木快速裂解气、液、固产物以及气相组分产率分布的影响,研究杨木快速裂解过程的反应机理,分析获得最大产油率的工艺操作条件。结果表明,杨木裂解过程中主要存在着生成焦油和生成焦炭两个反应的竞争和一个焦油二次裂化的连串反应,裂解温度、挥发性产物停留时间、升温速率决定着哪一种反应占据主要,从而得到安全不同的产物分布。     

薄层色谱和柱色谱实验教学的一点改进

薄层色谱和柱色谱是基础有机化学实验教学中的重要内容。文章通过对经典实验装置的改进,减少了有机溶剂的使用量,减少了环境污染,缩短了实验时间,丰富了教学内容。     

应用电子效应判断有机化学反应主要产物

诱导效应和共轭效应是高等有机化学中两类重要的电子效应,贯穿了大学有机化学的学习,一直是大学有机化学中的重点难点。本文通过分类分析和总结这两类电子效应对π电子的极化作用和中间体稳定性两方面的影响,可确定反应的主要产物,有利于学生的学习和相关内容掌握,为有机化学知识在反应生产中判断主要产物提供了重要的基础保障。涉及的反应包括亲电加成反应、亲核加成反应和亲电取代反应等。     

对氨基苯磺酸制备的微型实验改进与探讨

苯胺与浓硫酸通过磺化反应来制备对氨基苯磺酸是有机化学实验教学中一个常见的反应。该实验常在烧瓶中进行高温反应制备。本文试管反应对微型反应进行了改进,优化了微型反应装置,增加了反应操控性和实验效果。     

单萜烯与硫酸产物的研究

单萜烯是工业和大气环境中一类重要的化合物。文章选择一系列单萜烯与硫酸溶液反应,产物种类差别不大,产物含量很大不同。从实验结果中可以得出:在相同的反应条件下,a-pinene的反应活性是最大的。通过ESI-MS检测产物分子量,主要分子量为136,所以单萜烯在酸性条件下主要发生重排异构反应。     

串联反应产物分布优化研究

在一定的工艺条件下,流动反应器内物料的返混影响着串联反应的产物分布.本文分别对串联反应在平推流管式反应器和完全混合流釜式反应器中各组分的分布规律进行了研究,通过对两种反应器进行比较,给出反应器选择和在实际生产中反应器设计及操作方式确定的建议.     

创新性有机化学实验——N-(对甲苯基)苯甲酰胺的合成

介绍了一个创新性有机化学实验--微波辐射下通过铁(Ⅲ)催化的转酰氨基合成N-(对甲苯基)苯甲酰胺,采用单因素法考察了催化剂种类、催化剂用量、微波功率、溶剂对反应产率的影响,确定了最佳反应条件。     

手性锰配合物仿生催化烯烃的不对称环氧化反应研究——有机化学综合实验设计及教学

手性锰配合物仿生催化烯烃的不对称环氧化反应是一个有机化学综合实验,由文献调研、有机化合物的合成、结构表征、催化反应条件优化等环节组成。该实验可以强化学生对有机化学基础知识的理解,使学生掌握实验操作技能,同时培养学生的动手操作能力、分析和解决问题的能力、团队协作意识和科研兴趣,对应用型人才的培养具有重要意义。     

Design and synthesis of new classes of heterocyclic C-glycoconjugates and carbon-linked sugar and heterocyclic amino acids by asymmetric multicomponent reactions (AMCRs)

While chemical efficiency relies on several factors, the multicomponent reaction (MCR) approach was considered as a powerful synthetic tool for preparing target molecules of biological relevance in an efficient manner. Four classes of new bioactive molecules were designed and synthesized by asymmetric MCRs, in some cases with the cooperation of polymer-assisted solution-phase (PASP) technique. These include (a) C-glycosyl dihydropyrimidines and dihydropyridines via Biginelli and Hantzsch cyclocondensations, (b) C-glycosyl beta-amino acids via Mannich- and Reformatsky-type reactions, (c) C-glycosyl beta-lactams via Staudinger reaction, and (d) heterocyclic alpha-amino acids (glycine and alanine) via the Biginelli and Hantzsch reactions.     

三氟甲磺酸盐催化多组分人名反应

多组分化学反应具有操作简单、高效率和高原子经济性等优点,是一类重要的收敛性合成方法。三氟甲磺酸盐作为新型Lewis酸催化剂有极高的耐热性和耐氧化还原性,水相有机相均可催化,因温和、环境友好、可循环使用等特点而受到广泛关注。利用三氟甲磺酸盐催化多组分化学反应已经成为绿色化学的重要手段之一。简要总结了三氟甲磺酸盐催化剂在Strecker反应、Ha-ntzsch反应、Biginelli反应、Mannich反应、Passerini反应和Ugi反应等人名反应中的应用情况,并对其面临的挑战和机遇进行了讨论和展望。     

Comparative study using different infrared zones of the solventless activation of organic reactions

In this work, the results of a study comparing the use of irradiation from different regions of the infrared spectrum for the promotion of several organic reactions, are presented and discussed. This use of eco-conditions provides a green approach to chemical synthesis. A set of ten different organic reactions were evaluated, including the Knoevenagel, Hantzsch, Biginelli and Meldrum reactions. It is important to highlight the use of a commercial device that produces infrared irradiation in the near infrared region and its distribution by convection providing heating uniformity, significantly reducing reaction times, achieving good yields and proceeding in the absence of solvent. It is also worth noting that a variety of different reactions may be performed at the same time. Finally, the products obtained were identified using TLC, together with corresponding MS-data, complementarily in comparison of NMR (1)H and (13)C data with literature information.     

Greener,solvent free three component Biginelli reaction over different recyclable solid acid catalysts

Solid acids comprising 12-tungstophosphoric acid and 12-tungstosilicic acid anchored on to metal oxide (ZrO₂), zeolites (Hβ and HZSM-5), and mesoporous material (MCM-41) were synthesized, characterized and used as the catalysts. A solvent free green route to carry out the Biginelli cyclocondensation reaction is described over synthesized catalysts. The method provides an efficient and much improved protocol of Biginelli reaction in terms of solvent free conditions, high yields up to 98 %, very short reaction time of 15 min, and simple work-up procedure. Based on the above study a best catalyst among all is proposed and is recycled up to four times without any significant change in % yields of the product. Another important feature of this method is survival of a variety of functional groups under the reaction conditions.     

Urease: A highly biocompatible catalyst for switchable Biginelli reaction and synthesis of 1,4-dihydropyridines from the in situ formed ammonia

Urease is a superior biocompatible catalyst for switching from the Biginelli reaction to urea-based synthesis of 1,4-dihydropyridines in water, where 100% switching occurs at 0.02 g/mL of enzyme. Hantzsch reaction with ammonium acetate (NH₄OAc) is inefficiently catalyzed by urease (70%, 4 h), and heavy metal ions inhibit the urease-catalyzed reactions with urea or NH₄OAc. Promotion of the urea-based Hantzsch reaction by urease and its inhibition with Hg^2 + supports specificity of urease for in situ generation of ammonia, whereas the role of urease in further transformations is not so specific. The features of this enzymatic method are reusability, mild reaction conditions, biocompatibility, generality, and high yield of products.     

Synthesis of Dihydropyrimidinones Using Large Pore Zeolites

Abstract  

A series of dihydropyrimidin-2(1H)-one (DHPM) belongs to one of the important class of therapeutic and pharmacological active compound, were synthesized through the multicomponent reactions (MCRs) of aldehydes, ethyl acetoacetate and urea, followed by the heterogeneous catalyzed Biginelli reaction. In the present endeavour, medium (ZSM-5) and large pore zeolites (Y, BEA and MOR) as well as dealuminated zeolites BEA, were studied as catalysts. An excellent activity for DHPMs synthesis is achieved by optimizing accessibility of the reactants to the active sites and the surface polarity of zeolite catalysts. Moreover, the mechanism of Biginelli reaction was studied by means of GAUSSVIEW energy calculations of adsorbed acylimine intermediate on zeolite by using the density functional method (DFT).     

纳米二氧化硅负载磷钨酸催化合成2-十二烷基苯

采用纳米二氧化硅为载体,负载磷钨酸制备催化剂,催化合成制备2-十二烷基苯。实验表明:纳米二氧化硅负载磷钨酸制备的催化剂在烷基化反应中表现出很好的催化性能;优化的工艺条件为m(苯)∶m(1-十二烯)=8∶1,反应时间为2h,反应温度为80℃,催化剂负载量和加入量分别为20%(m/m)和2%(m/m,以反应物总量计);催化剂对苯与1-十二烯合成反应表现出较高活性和选择性。通过对反应产物进行高效液相色谱质谱联用仪分析,结果显示产物直链性较好。     

A study of the temperature effect on Hantzsch reaction selectivity using Mn and Ce oxides under solvent-free conditions

In this communication, four materials (CeO₂, CeO₂(Cu), MnO_x, and MnO_x(Cu)) were prepared, characterized and tested as catalysts, in solvent-free conditions, for the multicomponent Hantzsch reactions to obtain alternatively the 1,4-dihydropyridine or 2-phenylpyridine depending on the reaction conditions. 1,4-Dihydropyridine 4 was the main product formed at 80 °C (76%), and 2-phenylpyridine 7 was the main product at 40 °C (91%), in oxidant-free conditions, using CeO₂ catalyst. It is the first report that shows that, not only the temperature but also the nature of the catalyst may change the product selectivity in Hantzsch reactions.     

Polyaniline salts and complexes: Efficient and reusable catalyst for the one‐pot synthesis of 5‐(methoxycarbonyl)‐6‐methyl‐4‐phenyl‐3,4‐dihydropyrimidin‐2(1h)‐one

Polyaniline salts were prepared by doping polyaniline base with different Bronsted acids (sulfuric, nitric, phosphoric, perchloric, hydrochloric acid) and organic acids (p‐toluene sulfonic acid, 5‐sulfosalicylic acid). Polyaniline complexes were also prepared using Lewis acids (aluminum chloride, ferric chloride). Polyaniline salts and polyaniline complexes were used as catalysts in Biginelli reaction for 5‐(methoxycarbonyl)‐6‐methyl‐4‐phenyl‐3,4‐dihydropyrimidin‐2(1H)‐one synthesis. Benzaldehyde and urea were reacted with methyl acetoacetate using polyaniline‐p‐toluene sulfonate salt as catalyst with different reaction time, temperature, and amount of catalyst. The use of polyaniline catalysts is feasible because of the easy preparation, easy handling, stability, easy recovery, simple work‐up procedure, reusability, excellent activity with less amount of catalyst, and eco‐friendly nature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1741–1745, 2006     

Ceria-Supported Vinylpyridine Polymers: Synthesis,Characterization and Application in Catalysis

A simple, one-step synthesis of 4-vinylpyridine polymer crosslinked with 2% divinylbenzene [poly(4vp-dvb)] anchored with ceria nanocrystals via in situ reactions that involve simultaneous formation of the polymer and ceria nanocrystals is presented. The polymer support is formed by free radical suspension polymerization of the monomers, while ceria nanocrystals are generated from CeCl₃·7H₂O by the homogeneous precipitation method in a single pot. The polymer supports were characterized by XRD, TEM, SEM, ESCA, and TGA and then tested for their ability as heterogeneous recyclable catalysts in a Biginelli reaction. The catalytic activities of these supports were found to be far superior to the two-step conventional one and simultaneous microporous bead counterparts. Reusability is an added advantage over the other regularly used cerium-based catalysts in aqueous media. The significant increase in the catalytic activity is due to the higher Ce/N ratio and predominance of well-defined and more reactive exposed planes of ceria nanocrystals on the new supports. Such catalysts are of great importance due to environmental, practical and economical concerns.