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The carbon‐carbon and carbon‐heteroatom bond formation reactions are considered as a fundamental tool in synthetic organic chemistry. They have been effectively utilized in the synthesis of medicinally significant molecules, agrochemicals and valuable compounds in material sciences. This has been primarily enabled by highly efficient protocols arising from divergent mechanistic pathways. In this personal account, we aim to discuss some recent advances in carbon‐carbon or carbon‐heteroatom bond formation reactions to which our group has actively contributed. More specifically, this record focuses on the use of unsaturated carbon compounds for the construction of C?C and C?X bonds. 相似文献
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KOH/4A分子筛催化剂对环氧丙烷、二氧化碳和甲醇合成碳酸二甲酯反应的催化性能 总被引:4,自引:0,他引:4
首次开发出对环氧丙烷、二氧化碳和甲醇合成碳酸二甲酯反应具有较高活性和稳定性的KOH/4A分子筛固体催化剂,考察了反应温度和催化剂活性组分KOH的负载量等因素对催化剂性能的影响. 在优化的实验条件下,环氧丙烷可以完全转化,碳酸二甲酯的收率为168%. 从实验结果推测,产物碳酸二甲酯是由环氧丙烷和二氧化碳加成生成碳酸丙烯酯,然后与甲醇发生酯交换反应生成的,甲醇对环氧丙烷和二氧化碳合成碳酸丙烯酯反应具有助催化作用. 相似文献
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Synthesis of Substituted Pyrroles via Copper‐Catalyzed Cyclization of Ethyl Allenoates with Activated Isocyanides 下载免费PDF全文
Prof. Kui Lu Fang Ding Long Qin Xiaoliang Jia Chuanming Xu Prof. Xia Zhao Dr. Qingwei Yao Prof. Peng Yu 《化学:亚洲杂志》2016,11(15):2121-2125
A new method for the synthesis of di‐ and trisubstituted pyrroles via copper‐catalyzed cyclization of ethyl allenoates with activated isocyanides has been developed. In contrast to related annulation reactions previously reported, this new process features a skeletal rearrangement in which the aryl sulfonyl moiety, which functions as the electron‐withdrawing group in the α‐carbon of the isocyanide, was found to migrate to the γ‐carbon of the starting allenoate in the final product for the first time. 相似文献
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近年来,光催化裂解水产氢(H2)引起了广泛的关注.储量丰富,环境友好的非金属无机半导体β-SiC(立方相碳化硅)具有适当的带隙(Eg=2.4 eV,ECB=?0.9 V),是一种潜在的光催化剂.受限于SiC光催化剂内部光生电子-空穴对的快速复合,SiC光催化剂的效率较低.已有的关于SiC光催化剂改性的报道主要包括构建纳米SiC,构建SiC异质结,构建碳/SiC材料杂化材料.进一步的研究表明,SiC与碳材料之间通过紧密的界面接触形成了肖特基结,能将SiC表面的光生电子快速转移,抑制光生电子-空穴对的快速复合,从而提高光催化分解水产氢的活性.另一方面,碳纳米管(CNTs)具有良好的电子导电性,一维有序的管腔所形成的电子快速传导路径.因此,将半导体光催化剂与CNTs复合,是一种制备先进的光催化剂的有效策略.本文利用Si蒸气与CNTs之间的气-固反应,在CNTs表面原位生长SiC纳米包覆层,成功地制备了一维同轴核-壳CNTs@SiC纳米管.高分辨率透射电子显微镜图像表明,SiC与CNTs之间是通过Si-C共价键原子接触,并得到X射线光电子能谱的证实.将一部分CNTs@SiC纳米管在空气中750 oC煅烧2 h以除去CNTs,得到纯SiC纳米颗粒作为对比组.紫外-可见吸收光谱表明,CNTs能够促进SiC对光的吸收.荧光发射光谱(PL),瞬态荧光寿命测试,瞬态光电流测试以及交流阻抗(EIS)测试表明,CNTs能够促进SiC表面光生电子的传输与分离,有利于提升光催化效率.以0.1 mol/L Na2S溶液作为牺牲剂,在模拟太阳光(A.M 1.5)照射下,CNTs@SiC纳米管(不额外负载Pt等贵金属作为助剂)的产氢速率为118.5μmol g^-1 h^-1,是纯SiC纳米颗粒(21.1μmol g^-1 h^-1)的5.62倍.经过20 h的光照测试,CNTs@SiC纳米管的光催化性能无明显衰减;X射线衍射测试与扫描电子显微镜图像表明,CNTs@SiC纳米管的结构与形貌反应前后几乎无变化.莫特-肖特基测试表明,CNTs的费米能级比SiC低,因此SiC表面的光生电子能够快速地转移到CNTs,并且CNTs的良好导电性与一维有序的管腔所形成的长的电子传导路径能够进一步地增加电子寿命,促进光生电子参与光催化反应.另外,通过原子连接的同轴核-壳CNTs@SiC纳米管提供了大量且有效的电子传输路径.因此,与纯SiC纳米晶等同类材料相比,无机非金属CNTs@SiC纳米管具有更强的光催化氢活性. 相似文献
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Hydrous manganese oxide/carbon nanotube composite electrodes for electrochemical capacitors 总被引:2,自引:0,他引:2
A novel type of composite electrode based on hydrous manganese oxide and a single-walled carbon nanotube has been prepared and used in electrochemical capacitors. Cyclic voltammetry, galvanostatic charging/discharging tests and electrochemical impedance measurements were applied to investigate the performance of the composite electrodes with different ratios of hydrous manganese oxide and single-walled carbon nanotube. For comparison, the performance of pure hydrous manganese oxide and pure carbon nanotubes was also studied. In this way, the composite electrode with a 6:4 ratio of hydrous manganese oxide to carbon nanotube was found to be the most promising active material for an electrochemical capacitor, which shows both good capacitance and power characteristics. 相似文献
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From dielectric spectroscopy on mechanically sheared dispersions of carbon black in mineral oil it was known that the distribution of relaxation times was invariant irrespective of the applied shear rate. From this observation fractal behaviour was suspected and a small angle neutron scattering experiment was set up for confirmation. Indeed, by this experiment a fractal dimension has been found of d=2.19, a value which is perfectly comparable tod=2.0 found by dielectric spectroscopy.The dielectric behaviour of the smectite dispersion is different from the carbon black and small angle neutron scattering confirms this. Ad-value of 2.8 has been found, pointing to a more compact object than could be expected from a fractal. 相似文献
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In this work, an attempt has been made to modify the shape and nanostructure of core-shell materials, which have been usually generated on the basis of amorphous spherical cores. Novel core-shell silicate particles, each of which consists of a silicalite-1 zeolite crystal core and mesoporous shell (ZCMS), were synthesized for the first time. The ZCMS core-shell particles are unique because they are of pseudohexagonal prismatic shape and have hierarchical porosity of both a uniform microporous core and a mesoporous shell coexisting in a particle framework. The nonspherical bimodal porous core-shell particles were then utilized as templates to fabricate a new carbon replica structure. Interestingly, the pore replication process was carried out only through the mesopores in the shell, and not through the micropores due to the narrower micropore size in the core, resulting in nonspherical carbon nanocases with a hollow core and mesoporous shell (HCMS) structure. Nonspherical silica nanocases with HCMS structure were also generated by replication using the carbon nanocases as templates, which are not possible to synthesize through other synthetic methods. Interestingly, the pseudohexagonal prismatic shape of the zeolite crystals was transferred onto the carbon and silica nanocases. 相似文献
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Liu J Shao M Chen X Yu W Liu X Qian Y 《Journal of the American Chemical Society》2003,125(27):8088-8089
The bamboo-shaped carbon nanotubes were synthesized on a large scale through an ethanol thermal reduction process, in which ethanol was used as the carbon source and magnesium was used as the reductant. The toxic or corrosive reagents have been completely avoided. Furthermore, Y-junction carbon nanotubes obtained from our experiment can be used as the building blocks of nanoelectronics. Because of the simplicity and high yield of this route, it may potentially be applied on the scale of industrial production. 相似文献
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以"碳的结构与性能及其应用"为例说明元素化学课堂教学中的方法,引导学生在复习碳元素的结构与性质的基础上,组织学生开展课堂讨论,引导学生对不断涌现的新型碳材料的关注和兴趣。同时,分组讨论碳氧化物的结构与化学性质之间关系及其有效利用,即模拟光合作用实现CO2的光催化还原和基于费托合成实现CO为原料制备燃料,鼓励和推进学生开展碳材料及其应用的本科生科研训练,实现课堂知识与科学研究衔接。 相似文献
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The results of the thermokinetic analysis of the combustion of carbon containing materials in the air and oxygen have been
presented. A thermokinetic model has been developed, which simplifies the current approach assuming the0-th order and zero
activation energy for this process. The interpretation of the results makes possible the identification of the material (carbon
carrier) of the highest reactivity toward oxygen. This material was used as a component of the insulating grease fill for
the continuous slab caster (CSC) process. The application of the fill proves successful in the industrial practice.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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It has been found that the electrochemical activity of glutathione was increased greatly at the glassy carbon electrodes modified with 5,10,15,20-tetraphenylporphine ruthenium(II) carbenyl (RuTPP), meso-tetraphenylporphine copper(II) complex (CuTTP) and hemin. It has been also found that glutathione would enhance the electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) at a hemin glassy carbon electrode; the enhanced ECL intensity was linear with the concentration of glutathione in the range of 1 x 10(-7)-1 x 10(-4) mol l-1, based on which method for determination of glutathione has been developed. The detection limit of glutathione was 2 x 10(-8) mol l-1, and the relative standard deviation for 1 x 10(-6) mol l-1 glutathione was 2.7%. The mechanism for this ECL system has been proposed. 相似文献
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Flow field-flow fractionation (flow FFF), a separation technique for particles and macromolecules, has been used to separate carbon nanotubes (CNT). The carbon nanotube ropes that were purified from a raw carbon nanotube mixture by acidic reflux followed by cross-flow filtration using a hollow fiber module were cut into shorter lengths by sonication under a concentrated acid mixture. The cut carbon nanotubes were separated by using a modified flow FFF channel system, frit inlet asymmetrical flow FFF (FI AFIFFF) channel, which was useful in the continuous flow operation during injection and separation. Carbon nanotubes, before and after the cutting process, were clearly distinguished by their retention profiles. The narrow volume fractions of CNT collected during flow FFF runs were confirmed by field emission scanning electron microscopy and Raman spectroscopy. Experimentally, it was found that retention of carbon nanotubes in flow FFF was dependent on the use of surfactant for CNT dispersion and for the carrier solution in flow FFF. In this work, the use of flow FFF for the size differentiation of carbon nanotubes in the process of preparation or purification was demonstrated. 相似文献
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《Analytical letters》2012,45(10):1881-1886
Abstract Carbon dioxide has been found to enhance the chemiluminescence of a luminol system. A determination method for carbon dioxide in water was developed by applying this reaction to a continuous flow membrane-separation system. Concentrations of carbon dioxide as low as 0.04 μ g C /mL were determined. Membrane-separation effectively eliminates interferences from Co(II), Cr(III), Fe(III), and other ions which also enhance chemiluminescence. The relative standard deviation for this method was 2.8% (n=5) for 4.0 μ g C /mL and the time required for the analysis of one sample was 3.0 min. 相似文献
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Ford TA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(5):1151-1155
Using a number of potential models for the gas-phase structure of the trimer of carbon monoxide as a guide, ab initio molecular orbital calculations have been carried out on this aggregate in order to determine its probable structure and vibrational spectrum in cryogenic matrices. The Fourier transform infrared spectra of carbon monoxide trapped in argon and nitrogen matrices have been recorded and, on the basis of the results of the theoretical calculations, a search for possible absorptions which may be assigned to trimeric species has been undertaken. 相似文献
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Thomas A. Ford 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(5):1151-XXXIV
Using a number of potential models for the gas-phase structure of the trimer of carbon monoxide as a guide, ab initio molecular orbital calculations have been carried out on this aggregate in order to determine its probable structure and vibrational spectrum in cryogenic matrices. The Fourier transform infrared spectra of carbon monoxide trapped in argon and nitrogen matrices have been recorded and, on the basis of the results of the theoretical calculations, a search for possible absorptions which may be assigned to trimeric species has been undertaken. 相似文献