共查询到20条相似文献,搜索用时 125 毫秒
1.
本文应用ESCA,XRD,IR,NMR和化学分析等法对给电子体,特别是醚对3TiCl_3·AlCl_3催化剂表面改性作了研究。揭示了给电子体的诱导迁移作用,提出了含醚3TiCl_3·AlCl_3催化剂表面结构的模型——三层结构模型。在此基础上指出了给电子体不是在活性中心现场起作用,而是通过诱导迁移作用来改变表面结构,从而影响着催化剂的定向性。 相似文献
2.
本实验应用光电子能谱、红外光谱、核磁共振及溶剂剥离等方法证实了钛醚络合物可与3TiCl_3·AlCl_3催化剂发生固相反应。 TiCl_4·2Et_2O+2AlCl_3→TiCl_4+2AlCl_3·Et_2O 经钛醚络合物处理后的催化剂表面可用三层结构模型近似。钛醚络合物以其给电子体和Lewis酸两种组份影响着催化剂的性能。给电子体组份仍可产生诱导迁移作用,伴随固相反应还出现局域配位环境的变化,产生新的表面缺陷,这些皆有益于反应产物(四氯化钛)的键合负载。最后对高效载体型催化剂的研制也提出了一些设想。 相似文献
3.
4.
本实验应用光电子能谱、红外光谱、核磁共振及溶剂剥离等方法证实了钛醚络合物可与3TiCl_3·AlCl_3催化剂发生固相反应:
TiCl_4·2Et_2O+2AlCl_3→TiCl_4+2AlCl_3·Et_2O
经钛醚络合物处理后的催化剂表面可用三层结构模型近似。
钛醚络合物以其给电子体和Lewis酸两种组份影响着催化剂的性能。给电子体组份仍可产生诱导迁移作用, 伴随固相反应还出现局域配位环境的变化, 产生新的表面缺陷, 这些皆有益于反应产物(四氯化钛)的键合负载。
最后对高效载体型催化剂的研制也提出了一些设想。 相似文献
TiCl_4·2Et_2O+2AlCl_3→TiCl_4+2AlCl_3·Et_2O
经钛醚络合物处理后的催化剂表面可用三层结构模型近似。
钛醚络合物以其给电子体和Lewis酸两种组份影响着催化剂的性能。给电子体组份仍可产生诱导迁移作用, 伴随固相反应还出现局域配位环境的变化, 产生新的表面缺陷, 这些皆有益于反应产物(四氯化钛)的键合负载。
最后对高效载体型催化剂的研制也提出了一些设想。 相似文献
5.
固体催化剂表面的酸性及其测定法 总被引:3,自引:0,他引:3
以固体为催化剂的异相催化反应可以分为离子型和电子型两大类;石油以及化学工业中許多是以酸性固体如H_3PO_4——硅藻土、AlCl_3-Al_2O_3,SiO_2-Al_2O_3等为催化剂的反应,如裂解、异构、烃化、聚合等都是离子型的。最近所得烃类在这些催化剂表面上的化学吸 相似文献
6.
7.
到目前为止,芳烃的烃化反应应用最广的催化剂仍为BF_3,AlCl_3及H_2SO_4等,它们的缺点是副反应和二次反应较多。因此,探索选择性更高的催化剂,仍然是十分引人注意的研究裸题。我们发现,卤代烷基铝可作为以卤代烷进行芳烃烃化时的催化剂。在同一时期的文献中,只兄到一篇关于以卤代烷基铝作为用环己烯进行芳烃烃化的催化剂的报导。根据我们的初步结果,在有溴代乙基鲴倍牛物,即C_2H_5AlBr_2和(C_2H_5)_2AlBr的等分子混合物存在下,甲苯与溴乙烷作用,或苯与1-氯丙烷作用时,均能发生烃化反应,且其烃化产率、选择性及异构化性能均比AlCl_3的文献结果为高。 相似文献
8.
9.
多聚磷酸在有机合成化学上的应用 总被引:1,自引:0,他引:1
一多聚磷酸(Polyphosphoric acid)简称PPA。呈胶粘状颇似糖浆。近年来,在有机合成化学上时见被用作缩合剂或催化剂。其功能与AlCl_3、P_2O_5、H_2SO_4、H_3PO_4、HF和BF_3以及其它酸性试剂颇有相同之点,而付反应却 相似文献
10.
D.C.Trivedi和S.Srinivasan报道,用苯和萘制成了一种容易加工、导电性可以满足电池电极之用的共聚物。值得注意的是,制备这种共聚物的方法相当简单。利用无水AlCl_3为路易斯酸催化剂,无水CuCl_2为氧化 相似文献
11.
12.
[reaction: see text] Currently, there is a renewed interest in reactions that are catalyzed by organic compounds. Typical organic catalysts for acylation or transesterification reactions are based on either nucleophilic tertiary amines or phosphines. This communication discusses the use of nucleophilic N-heterocyclic carbenes as efficient transesterification catalysts. These relatively unexplored and highly versatile organic catalysts were found to be mild, selective, and more active than traditional organic nucleophiles. 相似文献
13.
Dr. Xiao‐Feng Wu 《化学:亚洲杂志》2012,7(11):2502-2509
The advantages of zinc catalysts, such as their low toxicity, low cost, and environmentally benignity, are encouraging organic chemists to explore their applications in organic synthesis. As a non‐redox metal, zinc catalysts have been investigated in redox reactions over the past few decades. Because of the importance of redox reactions, the interest in zinc catalysts, and the fact that no review on zinc‐catalyzed redox reactions has been published, herein, I have collected and summarized the main contributions in this area. This review is divided into two parts: reduction reactions and oxidation reactions. 相似文献
14.
Over the last ten years there has been a huge increase in development and applications of organocatalysis in which the catalyst acts as a nucleophile. Amidines and guanidines are often only thought of as strong organic bases however, a number of small molecules containing basic functional groups have been shown to act as efficient nucleophilic catalysts. This tutorial review highlights the use of amidine, guanidine, and related isothiourea catalysts in organic synthesis, as well as the evidence for the nucleophilic nature of these catalysts. The most common application of these catalysts to date has been in acyl transfer reactions, although the application of these catalysts towards other reactions is an increasing area of interest. In this respect, amidine and guanidine derived catalysts have been shown to be effective in catalysing aldol reactions, Morita-Baylis-Hillman reactions, conjugate additions, carbonylations, methylations, silylations, and brominations. 相似文献
15.
Organic catalysts have found wide applications in organic synthesis. Many organic reactions, which originally do not occur under normal conditions or are difficult to operate normally, have been successfully conducted under mild conditions in the presence of catalysts. In recent years, 2,4,6-trichloro-1,3,5-triazine (TCT, cyanuric chloride) has been used as organic catalyst in many organic synthesis, because it is stable, nonvolatile, inexpensive, commercially available, and easy to handle. On account of these properties it has been used as a green catalyst and sometimes is a catalyst of choice in organic reactions. 相似文献
16.
In this review, we present an assessment of recent advances in alkyne functionalization reactions, classified according to different classes of recyclable catalysts. In this work, we have incorporated and reviewed the activity and selectivity of recyclable catalytic systems such as polysiloxane-encapsulated novel metal nanoparticle-based catalysts, silica–copper-supported nanocatalysts, graphitic carbon-supported nanocatalysts, metal organic framework (MOF) catalysts, porous organic framework (POP) catalysts, bio-material-supported catalysts, and metal/solvent free recyclable catalysts. In addition, several alkyne functionalization reactions have been elucidated to demonstrate the success and efficiency of recyclable catalysts. In addition, this review also provides the fundamental knowledge required for utilization of green catalysts, which can combine the advantageous features of both homogeneous (catalyst modulation) and heterogeneous (catalyst recycling) catalysis. 相似文献
17.
Susanta Hazra Ekta Malik Abhishek Nair Vikas Tiwari Pritam Dolui Anil J. Elias 《化学:亚洲杂志》2020,15(13):1916-1936
Designing reactions in aqueous media has been one of the major challenges in modern organic synthesis, especially to avoid the use of large amounts of organic solvents whose disposal is a matter of grave concern from an environmental perspective. The oxidation of alcohols and amines is an essential and important step in the synthesis of many valuable products including polymers and pharmaceuticals. In recent times, there has been a surge in the use of water as a solvent in many organic reactions. This review focuses specifically on the oxidation reactions of alcohols and amines carried out in water media using transition metal catalysts, metal‐free catalysts and photocatalysts. 相似文献
18.
Interface Engineering in Two‐Dimensional Heterostructures: Towards an Advanced Catalyst for Ullmann Couplings 下载免费PDF全文
Dr. Xu Sun Haitao Deng Prof. Wenguang Zhu Zhi Yu Prof. Changzheng Wu Prof. Yi Xie 《Angewandte Chemie (International ed. in English)》2016,55(5):1704-1709
The design of advanced catalysts for organic reactions is of profound significance. During such processes, electrophilicity and nucleophilicity play vital roles in the activation of chemical bonds and ultimately speed up organic reactions. Herein, we demonstrate a new way to regulate the electro‐ and nucleophilicity of catalysts for organic transformations. Interface engineering in two‐dimensional heteronanostructures triggered electron transfer across the interface. The catalyst was thus rendered more electropositive, which led to superior performance in Ullmann reactions. In the presence of the engineered 2D Cu2S/MoS2 heteronanostructure, the coupling of iodobenzene and para‐chlorophenol gave the desired product in 92 % yield under mild conditions (100 °C). Furthermore, the catalyst exhibited excellent stability as well as high recyclability with a yield of 89 % after five cycles. We propose that interface engineering could be widely employed for the development of new catalysts for organic reactions. 相似文献
19.
Dr. Milan Pramanik Michael G. Guerzoni Dr. Emma Richards Prof. Dr. Rebecca L. Melen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(9):e202316461
The development of new methods for enantioselective reactions that generate stereogenic centres within molecules are a cornerstone of organic synthesis. Typically, metal catalysts bearing chiral ligands as well as chiral organocatalysts have been employed for the enantioselective synthesis of organic compounds. In this review, we highlight the recent advances in main group catalysis for enantioselective reactions using the p-block elements (boron, aluminium, phosphorus, bismuth) as a complementary and sustainable approach to generate chiral molecules. Several of these catalysts benefit in terms of high abundance, low toxicity, high selectivity, and excellent reactivity. This minireview summarises the utilisation of chiral p-block element catalysts for asymmetric reactions to generate value-added compounds. 相似文献
20.
The development of cheap, effective and heterogeneous catalysts remains a substantial challenge in organic synthesis. Of the extensive heterogeneous catalysis, biochar materials have attracted increasing attention to be considered as an important class of support materials in organic reactions due to their distinctive characteristics such as high porosity, large specific surface area, high adsorption ability, excellent cation exchange capacity and outstanding stability. This review highlights recent advances over the past 5 years, outlining the synthetic methods of biochar materials and their applications as catalysts or catalyst supports in a range of organic reactions including oxidation, reduction, esterification, coupling, alkylation and multi-component reactions. 相似文献