非金属元素硒的同素异形体*

结合史实文献和最新研究成果,汇总了硒的同素异形体,可分为气态硒、液态硒、固体硒、纳米硒和硒团簇等5类,重点介绍了固体硒、纳米硒和硒团簇的种类、结构、性质、制备和应用等。完善了硒同素异形体在教学中的深入介绍,有助于体现科学研究对本科教学内容改革的推进作用。     

非金属元素的同素异形体(一)——氢和硼的同素异形体概述

进行了同素异形体概念的探讨。简要叙述了氢和硼2种典型非金属元素形成的各种同素异形体的存在、组成以及结构、制备和性质,首次将多种硼富勒烯、硼纳米管、硼单层平面等晶态硼的内容补充在硼的同素异形体中,并强调了计算化学对同素异形体的预测和现代科学技术发展对制备的作用及其在材料中的应用。     

非金属元素的同素异形体(二)——再谈碳的同素异形体

以“同一元素的不同形态的纯单质互称同素异形体”来定义,对数目众多的碳的同素异形体进行了归纳,它们可分为石墨、金刚石、富勒烯碳原子簇和新型纳米材料等4类。简要叙述了各种同素异形体的存在、组成、结构、制备、性质,并强调了计算化学对同素异形体的预测和现代科学技术发展对制备的作用及其在材料中的应用。     

非金属元素同素异形体化学(三)——硅的同素异形体

对数目众多的硅的同素异形体进行了全面归纳,它们可分为硅纳米晶的不同物相类、纳米结构硅物质、硅原子簇和硅烯等4大类。简要叙述了各种同素异形体的存在、组成和结构、制备和性质,并强调了计算化学对同素异形体的预测和现代科学技术发展对制备的作用及其在材料中的应用。     

同素异形体与多晶型体

在化学教学中,特别是在讨论元素单质性质时,常常使用术语"同素异形体".然而不同的教科书对"同素异形体"下了不同的定义,即使同一作者对"同素异形体"也作了不同的解释.这样就使得"同素异形体"的概念变得模糊起来,更为重要的     

具有螺共轭结构的碳的同素异形体:glitter碳

介绍碳的新的同素异形体glitter碳的结构及螺共轭特征,对碳的同素异形体的结构进行了比较。     

诺贝尔奖宠儿——碳元素的前世今生

碳元素历史悠久,与现代人类社会联系紧密,对人类未来意义重大,多次斩获诺贝尔奖。在揭开碳元素的发现史之后,介绍了活性炭、碳纤维、玻璃碳等无定形碳以及热解炭等过渡碳的重要作用。此外,晶形碳的经典同素异形体--C60富勒烯、碳纳米管、石墨烯的独特结构造就了其在纳米材料领域的非凡用途;新型同素异形体的合成、发现与应用更是碳元素研究领域的热点。     

也谈同素异形体互变是化学变化吗?

读了贵刊(1988.5)林昌必同志关于“同素异形体互变是化学变化吗?”一文后,笔者受益非浅,同时对该文所作的“……同素异形体的互变应是化学变化”这一结论持有不同的意见,特提出与林昌必同志商榷。     

金属锡的同素异形体

从传统白锡、灰锡到新型低维锡烯、锡量子点,归纳总结了第四主族元素锡的各种同素异形体,介绍了其结构、制备、性质及应用等方面,进一步丰富了无机金属元素同素异形体的学习。     

非金属元素氮的同素异形体概述

依据全氮物质的研究进展对非金属氮元素的同素异形体进行了归纳,按结构不同可将其分为分子氮、聚合氮、金属氮和原子簇氮等4类.分别对各种同素异形体的组成、结构、存在与合成进展以及应用进行了综合介绍,为丰富氮元素的教学和扩展应用研究提供重要素材.     

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%.     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

关于"对‘燃料电池物理及化学性能的有限时间热力学分析方法'的讨论”答复

把有限时间热力学理论用于化学过程的研究,将会得到一系列新的结论,开展这方面的研究是很有意义的.文献[1]以燃料电池为例,在同时考虑化学反应及传热不可逆性的情况下,研究了燃料电池的性能界限,文献[2]指出了文献[1]计算化学反应及传热不可逆性而引起系统与有关环境的总熵产生率的错误以及由此而导致的结论所存在的问题,并进行了富有启发性的分析与讨论.但文献[2]对于系统与有关环境的总熵产生率的计算也是不正确的,由此得到的其它结论自然不能成立.本文将就此情况下系统与有关环境的总熵产生率的计算再次进行讨论,并给出电池功率和效率的有限时间热力学性能界限.