高教版《基础有机化学》中两个还原反应机理的修正与补充

在教学过程中发现高等教育出版社出版的《基础有机化学》一书中有两个经自由基负离子的还原反应(即炔烃用碱金属和液氨还原反应和Birch(伯奇)还原反应)机理有不妥和需要完善之处,对此进行了修正与补充。     

电解液调控CO2电催化还原性能微观机制的研究进展

二氧化碳(CO₂)排放导致了严重的温室效应, 但作为重要的碳资源, CO₂电催化还原合成化学品因反应条件温和、 反应产物可调及可有效利用分布式电能等优势而备受关注. 在该反应体系中, 电解液作为反应介质, 可提供质子和反应微环境, 影响分子/离子传输. 因此, 构建新型电解液体系对于提高CO₂电催化还原产物的选择性和电流密度起到重要作用. 本文综合评述了CO₂电催化还原过程中电解液的作用和研究现状, 重点总结了水系电解液中阴阳离子(碱金属阳离子、 卤素离子等)和离子液体电解液对CO₂溶解度、 界面双电层结构(pH值、 电场效应)和中间体稳定性等的影响机制, 揭示了其调控对反应产物的选择性、 电流密度等的影响规律. 最后, 对电解液调控CO₂电催化还原性能的研究进行了展望.     

生物质再燃异相还原NO的分子模拟

基于密度泛函理论和过渡态理论,在分子水平上对焦炭异相还原NO以及碱金属钠的作用机理进行探究。结合单点能的零点能校正以及过渡态的虚频验证,发现钠能够有效促进焦炭对于第一个NO分子的吸附。尽管钠不能改变反应步骤,但可将焦炭异相还原NO决速步的活化能由121.04 kJ/mol降至100.62 kJ/mol;钠的存在使焦炭异相还原NO的指前因子增大且反应速率加快,增加了焦炭边缘的活性位点,强化了焦炭对于NO的异相还原性能。     

5β,3α-羟基-7-羰基-胆烷酸的还原反应

鹅去氧胆酸(2)经氧化得到5β,3α-羟基-7-羰基-胆烷酸(3),3的还原反应是制备熊去氧胆酸(1)的关键步骤。本文报道用碱金属和几种金属硼氢化物对3进行还原的结果。同时对两类不同还原剂的反应机理作了讨论。     

CO和O2气氛下煤中矿物质对NO—半焦还原反应的影响

在石英固定床反应器上采用程序升温法（TPR）分别考察了CO和O2气氛下煤中矿物质对NO－半焦还原反应的影响，研究了结果表明，CO和O2对于半焦还原NO的反应有显著的促进作用；煤中矿物的催化作用与其组成相关，矿物质中的碱金属Na对于NO－半焦反应具有较强的催化作用而对于CO－NO反应的催化作用较小；矿物质中的Fe对半焦还原NO的反应催化作用微弱，但在CO气氛下，Fe对于NO－CO反应的催化作用较强可有效地促进NO的还原以及O2－半焦反应形成的CO2在矿物质和半焦的催化下也参与还原NO；矿物质的惰质组分对Fe的催化作用以及NO－半焦反应均具有一定的阻抑作用。     

炔烃与Na/NH_3的还原反应不是催化氢化

某些有机化学教科书,甚至一些使用较广的教科书。都把在液氨中用金属钠还原炔烃得到烯烃这一反应编写在催化氢化的标题下,与用 Lindlar 催化剂的炔烃的部分氢化反应相提并论,而不加以任何说明。甚至用如下的方程式表述这一反应:N_(?)+NH_(?)(液氨)→XaNH_(?)+(1/2)H_(?)(?)这往往给读者造成两点误解。其一,把这一反应认为是催化氢化反应;其二,认为氢化所需的氢来自于钠与液氨生成氨基钠和氢气的反应。实际上此反应不是催化氢化反应,其反应历程应为 C≡C 被钠原子提供的两个电子所还原,第一个电子进入反键的π轨道,生成一个游离基负离子(Ⅰ),此负离子是强碱,     

铁基双金属材料还原降解三溴甲烷的研究

本文制备了Cu/Fe和Pd/Fe两种铁基双金属材料,考察它们对溴仿(CHBr_3)的还原去除效果。结果表明,溴仿的还原去除效果都随双金属材料投加量的增加而增加;溶液中H~+浓度越高,越有利于还原反应的进行;溶解氧的存在会对还原去除反应产生抑制作用。双金属材料与溴仿的还原去除反应包括直接还原和间接还原两种途径。Pd和Cu通过与零价铁组成原电池结构加快了零价铁在水中的腐蚀速度,从而增强了零价铁对溴仿的直接还原去除效果。Pd与Cu相比,具有更高的氢过电位,氢气更容易在Pd的表面生成,而氢气也可以作为还原剂,取代溴仿分子中的溴原子,完成还原脱卤。因此,Pd/Fe双金属材料对溴仿的还原去除效果要好于Cu/Fe双金属材料。     

含不同碱金属杂多酸盐催化剂氧化还原性的ESR研究

用ＥＳＲ法研究了异丁醛一步氧化制甲基丙烯酸过程中所用杂多酸盐催化剂的氧化－还原特性，得到含不同碱金属杂多酸盐催化剂的还原－再氧化处理后的ＥＳＲ谱，讨论了不同碱金属对催化剂氧化还原特性的影响，比较了催化剂中过渡金属离子Ｃｕ，Ｖ，Ｍｏ的氧还原能力，分析了Ｃｕ＾＋易氧化性能对催化反应速度的影响。     

聚苯胺衍生Fe-N-C催化剂在碱性电解质中对氧还原反应的催化性能

经过热解聚苯胺、碳和FeCl₃的混合物制备的Fe-N-C材料在酸性电解质中对氧还原反应表现出高的催化活性;由于材料中不存在任何贵金属, 因而被认为是一类新型非贵金属氧还原催化剂. 然而这类催化剂在碱性电解质中催化氧还原反应的性能如何尚不清楚. 本文使用旋转圆盘电极技术考察了制备的两个Fe-N-C催化剂在KOH水溶液中催化氧还原反应性能, 发现这两个催化剂表现出比无金属的N掺杂碳材料更高的活性. 与商业Pt/C催化剂相比, 它们催化氧还原反应的起始电势和半波电势分别仅低60和40 mV左右, 计时电流测试表明, 它们比Pt/C催化剂显示出更好的稳定性. 此外, 在这两个Fe-N-C催化剂上的氧还原反应主要遵循四电子途径. 本工作显示, Fe-N-C材料有望用于碱性燃料电池氧还原反应催化剂.     

氯化物熔盐中钕离子在铂电极上的电化学还原

利用极谱,Ⅲ利用电位阶跃研究了轻稀土离子在碱金属氯化物熔盐中的阴极还原。本文作者研究过Sm~(3 )在NaCl-KCl熔盐中的电还原。上述工作分别提出了稀土离子一步还原和分步还原的结论。本文采用线性扫描伏安法和恒电位电解,并配以扫描电子显微镜X射线能谱分析,对Nd~(3 )在Pt电极上的阴极还原过程进行了研究,利     

ELECTRON TRANSFER REACTIONS OF METAL CARBONYL ANIONS

Abstract

Metal carbonyl anions exhibit one- and two-electron reactions. The two-electron processes involving transfer of groups (hydrogen, alkyl, and halogen) between metal centers are related to the nucleophilicity. The one-electron processes are primarily outer-sphere electron transfer for the metal carbonyl anions. These reactions are observed in the presence of oxidants such as coordination complexes, pyridinium salts, metal carbonyl dimers and metal carbonyl clusters. However, in contrast to organic reactions, the metal carbonyl anions may undergo inner-sphere electron transfer. Reactions of metal carbonyl anions of low nucleophilicity with metal carbonyl cations or halides are best interpreted as inner-sphere, one-electron transfer.     

Separation of metal ions and metal-containing species by micellar electrokinetic capillary chromatography, including utilisation of metal ions in separations of other species

The use of micellar electrokinetic capillary chromatography (MEKC) for the separation of metal ions and metal-containing species is reviewed, together with the use of metal ions as a means to separate other species. Topics covered include the manipulation of separation selectivity through the use of complexation reactions induced by addition of a metal ion to the background electrolyte, enantiomeric separations facilitated through metal-analyte interactions, separation of organometallic species, separation of stable metal complexes in which the entire complex is the analyte and the separation of metal ions as analytes using pre-capillary or on-capillary complexation reactions with a suitable ligand.     

Application of solid-state early-transition metal clusters as catalysts

Metal cluster compounds are expected to be catalysts for new reactions because of synergistic effect of the metal atoms. In solid-state halide clusters and sulfide clusters, metal cluster frameworks are linked in two- or three-dimensions to form a cluster network. Halogen- or sulfur-deficient metal sites in an octahedral metal cluster framework are retained intact and act as catalytically active sites even at high temperatures of 400–700?°C. This review reports recent advances in the development of coordinatively unsaturated metal atoms on solid-state clusters with an octahedral metal framework and their application to organic catalytic reactions.     

Carbon-Carbon Bond Formation from Carbon Monoxide and Hydride: The Role of Metal Formyl Intermediates**

Current examples of carbon chain production from metal formyl intermediates with homogeneous metal complexes are described in this Minireview. Mechanistic aspects of these reactions as well as the challenges and opportunities in using this understanding to develop new reactions of CO and H₂ are also discussed.     

Recent Advances on Confining Noble Metal Nanoparticles Inside Metal-Organic Frameworks for Hydrogenation Reactions

Hydrogenation reaction is one of the pillars of the chemical industry for the synthesis of drugs and fine chemicals. To achieve high catalytic performance, it is still highly desirable for constructing novel supported metal catalysts. Different from conventional supports like metal oxides, zeolites and carbon materials, metal-organic frameworks(MOFs) as the emerging porous materials have Hexhibited great potential to host metal nanoparticles (NPs) for achieving hydrogenation reactions with high catalytic efficiency, due to their unique porous structures. Recently, many progresses have been made, and thus, it is necessary to summarize the recent progresses on confining metal NPs inside MOFs for hydrogenation reactions. In this review, we first introduced the general synthesis methods for confining noble metal NPs inside MOFs. Then, the applications of noble metal NPs/MOFs catalysts in hydrogenation reactions were summarized, and the synergistic catalytic performances among noble metal NPs, metal nodes, functional groups, and pore channels in MOFs were illustrated. Subsequently, the hydrogen spillover effect involved in the hydrogenation reactions was discussed. Finally, we provide an outlook on the future research directions and challenges of confining noble metal NPs inside MOFs for hydrogenation reactions.     

New perspective of electron transfer chemistry

A new perspective of electron transfer chemistry is described for fine control of electron transfer reactions including back electron transfer in the charge separated state of artificial photosynthetic compounds and its synthetic application. Fundamental electron transfer properties of suitable components of efficient electron transfer systems are described in light of the Marcus theory of electron transfer, in particular focusing on the Marcus inverted region, and they are applied to design multi-step electron transfer systems which can well mimic the function of a photosynthetic reaction center. Both intermolecular and intramolecular electron transfer processes are finely controlled by complexation of radical anions, produced in the electron transfer, with metal ions which act as Lewis acids. Quantitative measures to determine the Lewis acidity of a variety of metal ions are given in relation to the promoting effects of metal ions on the electron transfer reactions. The mechanistic viability of metal ion catalysis in electron transfer reactions is demonstrated by a variety of examples of chemical transformations involving metal ion-promoted electron transfer processes as the rate-determining steps, which are made possible by complexation of radical anions with metal ions.     

The Kharasch type reaction of allylic halides with Grignard reagent in the presence of transition metal halides

The reaction of allylic halide with Grignard reagent in the presence of transition metal chloride has been investigated. Three reactions of allylic halide occurred competitively; (i) reduction to olefin, (ii) coupling with Grignard reagent to olefin (cross-coupling) and (iii) coupling with itself to 1,5-diene (homo-coupling). The relative importance of these reactions depends on both the structures of allylic halide and Grignard reagent, as well as on the transition metal salt utilized. The mechanism was discussed in terms of the allylic transition metal intermediate.     

气相中Y＋, Zr＋, Nb＋与CO2反应的理论研究

以Y^＋, Zr^＋, Nb^＋与CO₂反应作为第二前过渡金属离子与CO₂反应的范例体系. 采用密度泛函UB3LYP方法, 对于Y, Zr, Nb采用Stuttgart赝势基组, 对于CO₂采用6-311＋G(2d)基组, 计算研究了三种金属离子在基态和激发态时与CO₂气相反应的机理. 结果表明三种金属离子与CO₂反应以高自旋进入反应通道, 在反应过程中发生系间窜越, 以低自旋中间体和最终产物离开反应通道. 用内禀坐标单点垂直激发计算的方法找到了势能面交叉点, 并作了相应的讨论. 因为有金属离子的参与, 使单分子CO₂的强吸热分解反应变为生成CO和MO^＋的放热过程.     

Three characteristic reactions of alkynes with metal compounds in organic synthesis

Alkynes have two sets of mutually orthogonal π‐bonds that are different from the π‐bonds of alkenes. These π‐bonds are able to bond with transition metal compounds. Alkynes easily bond with the various kinds of compounds having a π‐bond such as carbon monoxide, alkenes, other alkynes and nitriles in the presence of the transition metal compounds. The most representative reaction of alkynes is called the Pauson–Khand reaction. The Pauson–Khand reactions include the cyclization of alkynes with alkenes and carbon monoxide in the presence of cobalt carbonyls. Similar Pauson–Khand reactions also proceed in the presence of other transition metal compounds. These reactions are the first type of characteristic reaction of alkynes. Other various kinds of cyclizations with alkynes also proceed in the presence of the transition metal compounds. These reactions are the second type of characteristic reaction of alkynes. These include cyclooligomerizations and cycloadditions. The cyclooligomerizations include mainly cyclotrimerizations and cyclotetramerizations, and the cycloadditions are [2 + 2], [2 + 2 + 1], [2 + 2 + 2], [3 + 2], [4 + 2], etc., type cycloadditions. Alkynes are fairly reactive because of the high s character of their σ‐bonds. Therefore, simple coupling reactions with alkynes also proceed besides the cyclizations. The coupling reactions are the third type of characteristic reactions of alkynes in the presence of, mainly, the transition metal compounds. These reactions include carbonylations, dioxycarbonylations, Sonogashira reactions, coupling reactions with aldehydes, ketones, alkynes, alkenes and allyl compounds. Copyright © 2008 John Wiley & Sons, Ltd.     

Dissolution of oxygen reduction electrocatalysts in an acidic environment: density functional theory study

Density functional theory is employed to determine the reaction thermodynamics of a group of chemical and electrochemical reactions chosen to investigate the dissolution of metal atoms from oxygen reduction reaction catalysts in an acid medium. Once a set of thermodynamically allowed reactions is established, those reactions are selected to investigate the relative stabilities of Pt atoms and of other transition metal atoms (Ir, Pd, Rh, Ni, and Co) toward the dissolution reactions. The dissolution reactions that are found thermodynamically favorable are electrochemical and involve adsorbed oxygenated compounds that are intermediate species of the oxygen reduction reaction. Iridium is found to be the most stable among the various pure metals in comparison to Pt. Most of the metals alloyed with Pt cause a decrease of the Pt stability against dissolution, except for Ni, which does not affect it. On the other hand, the influence of Pt on the stability of the second metal in the alloy follows the same trend as in pure metal catalysts, with Ir being the most stable. When both atoms in a PtM alloy are involved in dissolution reactions, alloyed Ir is also found more stable than Pt in a given dissolution reaction, and the same behavior is found in alloyed Co for most of the reactions studied.