亚稳态分子间复合物Al/Bi_2O_3及其应用

具有输出压力较高、燃烧效率高、能量释放速率快、安全环保等特点的亚稳态分子间复合物(MIC)Al/Bi_2O_3,在新型火工药剂、炸药和推进剂等含能材料研究领域具有良好的应用前景。本文系统概括了亚稳态分子间复合物Al/Bi_2O_3的反应机理模型、制备方法及其应用。首先介绍并比较了MIC的几种反应机理及模型,详述了目前能够较合理地解释和计算Al/Bi_2O_3输出压力的CJ爆轰模型和热平衡模型。然后综述了纳米Bi_2O_3及Al/Bi_2O_3的制备方法,通过改变制备方法可以获得不同形貌、结构和燃烧性能的纳米Al/Bi_2O_3。同时,分析了反应物粒径和添加物对纳米Al/Bi_2O_3燃烧性能的影响。此外,简要介绍了纳米Al/Bi_2O_3的应用研究进展。最后,对亚稳态分子间复合物Al/Bi_2O_3的研究现状进行了总结,并展望了未来可能的发展前景和方向。     

生物正交剪切反应及其应用

生物正交反应在化学生物学的研究中发挥着越来越重要的作用.传统的生物正交反应以新化学键生成的连接反应为主,其在实现生物分子的“标记”、“示踪”和“捕捉”等研究中发挥着重要作用.近年来,一类新兴的反应类型--以化学键断裂为基础的生物正交剪切反应逐渐发展起来,并在分子的“释放”、“激活”和“操控”等方面得到了越来越广泛的应用.本文首先重点介绍了生物正交剪切反应,总结了这些反应的特点、适用范围和已经实现的用途.随后通过具体的例子介绍了这些反应在化学生物学中的应用,包括小分子前药的激活、蛋白质功能的调控、细胞的工程化等.最后文章对生物正交剪切反应的发展趋势进行了展望.     

溯源辨析“活化分子”概念在化学教材中的角色定位*

“活化分子”作为国内化学教育领域广为人知的科学概念,在各类相关化学教材中都有介绍。然而在国外多种经典化学教材中却完全没有“活化分子”的概念,反映出国内外化学教育领域对化学反应速率理论相关知识点的处理上存在明显的差异与分歧。通过溯源关键历史文献,回顾了“活化分子”概念的形成及其在化学反应速率理论发展过程中的角色演变,指出“活化分子”概念已经退出反应速率理论的舞台,在教材中应更多地呈现其在科学史方面的价值,而不是科学价值。     

离子液体中制备无机材料

离子液体作为潜在的“绿色”溶剂,具有许多传统溶剂无法比拟的优异性能,在有机合成、催化、液液分离和萃取等领域引起了广泛的研究。而在离子液体领域无机材料的制备是一个较新的发展分支,现已利用其合成出多种具有独特结构和性能的无机材料。本文就离子液体在无机材料制备方面的应用及发展趋势进行了综述。目前,对于制备无机材料,离子液体主要是作为电解液、表面活性剂或溶剂,本文介绍了其在应用中的优缺点,并指出该领域未来的发展趋势是离子热合成和集模板-溶剂-反应物于一身的离子液体反应。     

烟气循环流化床同时脱硫脱硝试验及机理研究

实验制备了以粉煤灰、石灰为原料的高活性吸收剂, 并在其中加入氧化性M添加剂使之成为具有氧化能力的高活性吸收剂. 在烟气循环流化床上进行了同时脱硫脱硝试验, 研究了影响同时脱硫脱硝效率及钙利用率等的若干因素. 在最佳试验条件下, 脱硫效率和脱硝效率分别达到了95.5%和64.8%. 实验对反应后吸收剂中SO₂和NO的脱除产物进行了成分分析, 结果表明, 在脱除产物中除了有硫物种外还有大量氮物种, 利用扫描电子显微镜和X射线能谱仪对高活性吸收剂基本材料如粉煤灰、“富氧型”高活性吸收剂和反应后的“富氧型”高活性吸收剂进行了表面微区分析, 根据试验结果提出了“富氧型”高活性吸收剂的脱硫脱硝机理.     

水杨叉间溴缩苯胺的光发色和热消色反应过渡态

亚稳态的可控转换是未来信息记录分子器件原理,因此,人们对光致色变化合物合成和光化学行为研究感到兴趣。水杨叉缩苯胺及其部份衍生物的固体、固相溶液和Lan-gmuir-Blodgett膜(LB膜)呈现光致色变性质。质子迁移是水杨叉缩苯胺的光致色变和热消色反应机理,反应按协同机理进行,反应     

高压下β-HMX热分解机理的ReaxFF反应分子动力学模拟

采用ReaxFF反应分子动力学方法研究了不同压缩态β-HMX晶体(ρ=1.89、2.11、2.22、2.46、2.80、3.20 g·cm^-3)在T=2500 K时的热分解机理, 分析了压力对初级和次级化学反应速率的影响、高压与低压下初始分解机理的区别以及造成反应机理发生变化的原因. 发现HMX的初始分解机理与压力(或密度)相关. 低压下(ρ<2.80 g·cm^-3)以分子内反应为主, 即N－NO₂键的断裂、HONO的生成以及分子主环的断裂(C－N键的断裂). 高压下(ρ≥2.80 g·cm^-3)分子内反应被显著地抑制, 而分子间反应得到促进, 生成了较多的O₂、HO等小分子和大分子团簇. 初始分解机理随压力的变化导致不同密度下的反应速率和势能也有所不同. 本文在原子水平对高压下HMX反应机理的深入研究对于认识含能材料在极端条件下的起爆、化学反应的发展以及爆轰等具有重要意义.     

绿色有机合成化学专辑 前言

随着社会不断进步,如何使化学在创造物质财富的同时保护人类赖以生存的环境,确保人身健康和安全,实现可持续发展已成为无法回避的问题,这也是对化学工作者提出的严峻挑战。为此,化学家在20世纪90年代初,提出了与传统的治理污染完全不同的“绿色化学”的概念,即如何从源头上减少、甚至消除污染的产生,因此要求任何一个化学活动,包括化学原料的使用、化学和化工过程以及最终的产品,对人类的健康和环境都应该是友好的。近20年来,绿色化学得到了飞速的发展,已成为一个多学科交叉的新的研究领域,是“科技引领可持续发展”的重要内容。其中,符合“绿色化学”基本原理和目标的“绿色有机合成化学”的发展尤为引人关注。最近,Chemical Reviews,Accounts of Chemical Research等国际著名期刊相继以“绿色化学”为主题出版了专辑。 近年来,随着国家对绿色化学的日益重视,我国绿色有机合成化学领域的专家学者在包括不对称催化反应在内的高选择性及原子经济性有机反应、惰性化学键如C-H的活化及反应、均相催化剂的负载化以及绿色介质中的合成反应等研究方面取得了长足的进展,并在某些方面达到了国际领先的水平,在清洁的有机合成工艺及技术开发方面也显示了很好的发展势头。受《化学进展》编委会的委托,我们组编了这期“绿色有机合成化学”专辑。一方面是为了及时总结绿色有机合成化学研究领域的最新成就和发展趋势,另一方面也尽量全面反映我国科学家在这一领域已经取得的具有特色的研究成果以及面临的挑战,以期为推动我国绿色化学研究向更高和更深层次发展起到积极作用。 本专辑涵盖了绿色有机合成化学的多个方面,诸如水、离子液体和超临界流体等非传统反应介质中的有机催化反应;金属配合物、有机小分子和酶催化的不对称合成;基于C-H键活化的C-C键偶联反应;有机、无机及其杂化体负载的均相催化剂;环境友好的聚合反应以及绿色介质离子液体的应用等。这些内容体现了绿色化学关于有机合成反应的“原子经济性”、“催化性试剂优于当量性试剂”、“尽量避免不必要的衍生化步骤”、“尽量使用无毒的辅助物质”和“采用无毒或低毒的反应底物”等原则。既对当前绿色化学研究的一些热点问题及重要进展进行了讨论、总结和展望,也基本能够反映我国目前在这一领域的工作特色和主流发展趋势。 参与本专辑撰写的作者都是在有机合成化学一线长期从事相关研究工作的专家,尽管他们工作十分繁忙,但都尽心尽力地在很短的时间内完成了撰写任务。本专辑是所有参与作者的辛勤劳动和共同努力的结果,在此向所有的作者及期刊编辑部的辛勤工作表示衷心感谢。同时,受编者学识所限,在本专辑的组稿和编写过程中可能出现的一些差错,我们深感歉意,望读者不吝赐教。 范青华 王东 2010年6月于北京     

低共熔溶剂中三取代咪唑的绿色合成

以氯化胆碱和对甲苯磺酸为原料,制备了质子酸型低共熔物,并研究了其在“一锅法”制备2,4,5-三取代咪唑化合物反应中的催化活性。结果表明,该低共熔物制备简单、催化活性高、反应后处理简便且催化剂可回收使用。另外,对可能的反应机理也进行了探讨。该实验符合绿色化学的要求,涉及有机、分析等相关内容,并锻炼了萃取、熔点测定、重结晶等操作,具有显著的综合化学实验特征。     

亚稳分子O~2(b^1∑^+~g)猝灭反应研究

在流动余辉装置中,利用镍金属表面催化氧原子复合的方法,产生了高浓度的亚稳态O~2(b^1∑^+~g)。采用准一级近似的方法,测定了O~2(b^1∑^+~g)被15种分子猝灭的速率常数,其大小在10^-12～10^-14cm^3·molecule^-1·s^-1数量级范围内,用电子－振动(E-V)能量转移模型分析了各种分子猝灭反应的机理,结果表明猝灭速率常数的大小与试剂分子中的C----H,N---H以及O-----H键的数目密切相关;同时,我们的结果也表明,分子的其它特性将对O~2(b)的猝灭反应也起着重要的作用。     

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.     

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.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.