Co-MCM-41催化H2O2氧化4-甲基吡啶生成4-吡啶甲酸的反应条件及机理

研究了乙酸溶剂中无引发剂条件下,Co掺杂MCM-41催化过氧化氢（30%）氧化4-甲基吡啶的反应,催化剂表现出高底物转化率和产物吡啶甲酸选择性以及良好的再生性。 探讨了不同溶剂、反应时间、反应温度、催化剂用量等对H2O2氧化4-甲基吡啶反应的影响,确定较优反应条件为m（4-甲基吡啶)∶m（催化剂)=10∶1,V（4-甲基吡啶)∶V（冰醋酸)=1∶10,温度363 K,时间6 h。 该条件下4-甲基吡啶的转化率为96.5%,4-吡啶甲酸的选择性为91.4%。 探讨了可能的反应机理。     

Fixation of heterocumulenes. 1. A theoretical study on the irreversible reaction of CO(2) with a 2-lithio-1,3-dithiane

The mechanism of electrophilic addition of CO(2) to 2-lithio-2-phenyl-1, 3-dithiane-tetrahydrofuran-tetramethylethylendiamine, a Corey-Seebach "umpolungs" reagent for nucleophilic acylation, was investigated at the B3YLP/6-311+G//HF/6-31+G level of theory with specific solvation effects being included in the study. The overall reaction is exothermic by 18.8 kcal/mol and proceeds via precomplexation of the CO(2) (necessary for activation). The reaction barrier is calculated to be 11.9 kcal/mol (relative to the precomplex 2a) and represents a lower boundary for the activation energy. The reaction barrier is shown to originate from specific solvent effects. A detailed survey of the electronic effects governing the reaction is given. The ab initio results were then compared with semiempirical PM3 calculations, which were extended to include the heterocumulenes COS and CS(2). As expected, the reduced electrophilicity of these molecules leads to a higher activation barrier by retention of the same reaction mechanism.     

Lipase-catalyzed separation of the enantiomers of 1-substituted-3-arylthio-2-propanols

Optically active (R)- and (S)-1-substituted-3-(arylthio)propan-2-ols have been prepared in the reaction of the appropriate 2-(arylthiomethyl)oxiranes with chloride and azide anions followed by a lipase-catalyzed transesterification. The effects of the enzyme preparation as well as of the reaction conditions have been compared in terms of the enantiomeric excess of the obtained acetate and unreacted alcohol.     

13C and (2)H kinetic isotope effects and the mechanism of Lewis acid-catalyzed ene reactions of formaldehyde

13C and (2)H kinetic isotope effects were determined for the ene reaction of formaldehyde with 2-methyl-2-butene at natural abundance catalyzed by diethylaluminum chloride. The reactive methyl group exhibits a k(12)(C)/k(13)(C) of 1.006-1.009 and a k(H)/k(D) of approximately 1.22-1.23. The latter represents a combination of primary and secondary effects and is consistent with a significant primary deuterium isotope effect. A very close correspondence of the other isotope effects with the equilibrium isotope effects predicted for formation of a model intermediate cation is observed. An intermolecular deuterium isotope effect of 2.0-2.5 was observed under several reaction conditions in the Lewis acid-catalyzed reaction of formaldehyde with d(0)/d(12)-tetramethylethylene. The results are interpreted as supporting the reversible formation of an essentially classical open cation followed by rate-limiting proton transfer.     

一步法水热合成 TiO2纳米线及其光催化性能

以钛酸丁酯和异丙醇为原料, 采用一步法在NaOH溶液中水解后直接进行水热反应, 经焙烧处理, 得到TiO2纳米线. 采用扫描电子显微镜(SEM)、X射线衍射(XRD)和能谱分析(EDX)对产物进行了形貌、结构及成分的表征. 考察了不同水热温度、碱液浓度、水热反应时间及焙烧温度等因素对产物的影响. 结果表明, 获得较好形貌TiO2纳米线的最佳水热温度、碱液浓度和水热反应时间分别是180 ℃, 10 mol/L和24 h. 所得TiO2纳米线焙烧至950 ℃时仍为锐钛矿相, 说明本文制备方法迟滞了TiO2纳米线由锐钛矿相向金红石相的转变. 以甲基橙为目标降解物, 采用紫外-可见分光光度计研究了未掺杂和铕掺杂TiO2纳米线(Eu-TiO2)的光催化性能. 结果显示, 最佳掺铕量(摩尔分数)为1.6%. 在300 W紫外灯照射60 min时, 此掺铕量的TiO2纳米线对甲基橙溶液的降解率是未掺杂样品的1.5倍.     

Theoretical study of the mechanism of hydrogenation of side-on coordinated dinitrogen activated by Zr binuclear complexes ([(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2))

The reaction mechanism of the reduction of dinitrogen coordinated side-on to a binuclear Zr complex, [(eta(5)-C(5)Me(4)H)(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)) (T1), was investigated theoretically using a model complex, [(eta(5)-C(5)H(5))(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)) (A1), employing density functional theory calculations. The effectiveness of A1 in describing T1 was confirmed by comparing the structures, distributions of charge, and frontier molecular orbitals. Our calculations showed that A1 has a twisted structure, resembling that of T1, which results in similar properties. The calculations for A1 and its derivatives on H(2) addition clearly explain the reaction mechanism and the reaction path that T1 follows, as well as the experimentally required reaction conditions. The immediate reaction of the first and second H(2) additions produces [(eta(5)-C(5)Me(4)H)(2)ZrH](2)(mu(2),eta(2),eta(2)-N(2)H(2)) (T2), and this is explained by the barrier heights of the reaction, which were calculated to be 20.4 and 10.9 kcal/mol, respectively. The latter barrier was below that of A1 + 2H(2). Complex T2 may be the initial complex for further H(2) addition under proper conditions, or it could lose one H(2) molecule followed by H migration from the Zr site to the N site. Both reactions are expected to occur, because of the closeness of the barrier heights (25.1 and 36.5 kcal/mol, respectively). Gentle warming is required for further H(2) additions, which can be understood from the energetics as well. The high reactivity of T1 with H(2) has been discussed by the comparison of the calculation of A1 and another complex with different ligands, presenting an interesting indication on the effects of the ligands. These theoretical results and discussion explaining the experiment should provide insight into the nature of the hydrogenation mechanism.     

TiSiW_(12)O_(40)/TiO_2催化合成磷酸三甲苯酯的研究

应用TiSiW_(12)O_(40)/TiO_2催化剂合成磷酸三甲苯酯研究结果表明，该催化 剂具有较高的催化活性。考察了催化剂用量、反应温度和反应时间对酯产率的影响 。在典型反应条件（催化剂用量为原料总量的1.0%，反应温度为100-120 ℃，反应 时间为8h）下所得磷酸三甲苯酯的产率为85.5%。该催化剂易于回收且可重复使用 ，具有良好的活性稳定性。     

Vibrational effects on the reaction of NO(2)(+) with C(2)H(2): effects of bending and bending angular momentum

NO(2)(+) in six different vibrational states was reacted with C(2)H(2) over the center-of-mass energy range from 0.03 to 3.3 eV. The reaction, forming NO(+)+C(2)H(2)O and NO+C(2)H(2)O(+), shows a bimodal dependence on collision energy (E(col)). At low E(col), the reaction is quite inefficient (<2%) despite this being a barrierless, exoergic reaction, and is strongly inhibited by E(col). For E(col)> approximately 0.5 eV, a second mechanism turns on, with an efficiency reaching approximately 27% for E(col)>3 eV. The two reaction channels have nearly identical dependence on E(col) and NO(2)(+) vibrational state, and identical recoil dynamics, leading to the conclusion that they represent a single reaction path throughout most of the collision. All modes of NO(2)(+) vibrational excitation enhance both channels at all E(col), however, the effects of bend (010) and bend overtone (02(0)0) excitation are particularly strong (factor of 4). In contrast, the asymmetric stretch (001), which intuition suggests should be coupled to the reaction coordinate, leads to only a factor of approximately 2 enhancement, as does the symmetric stretch (100). Perhaps the most surprising effect is that of the bending angular momentum, which strongly suppress reaction, even though both the energy and angular momentum involved are tiny compared to the collision energy and angular momentum. The results are interpreted in light of ab initio and Rice-Ramsperger-Kassel-Marcus calculations.     

Al2O3-SiO2催化环己胺氧化制备环己酮肟

以Al2O3-SiO2为催化剂,用双氧水氧化环己胺制备了环己酮肟。考察了溶剂用量、催化剂用量、反应时间和反应温度等因素对催化性能的影响。结果表明,在溶剂乙腈与环己胺体积比为3∶1,催化剂质量分数31.0%,75℃反应5 h后的环己胺转化率为100%,环己酮肟选择性可达83.6%。并对环己胺催化氧化的反应机理作了初步的探讨。     

Zn(Oxin)2·2H2O纳米晶的固相化学反应合成及表征

随着纳米微粒研究的深入,对纳米超细微粒提出了不同的物理、化学特性需求,制备高纯、超细、均匀的纳米微粒,发展新型的纳米材料,就显得非常重要,而解决问题的关键在于研究、发展新的合成技术.通常,纳米微粒制备的要求是:表面洁净;粒子形状及粒径、粒度分布可控,防止粒子团聚;易于收集;有较好的稳定性;产率高.     

Importance of entropy in the diastereoselectivity of 5-substituted 2-methyladamant-2-yl cations

The diastereofacial selectivity of 2-methyl-5-X-adamant-2-yl cations IX (X = CN, Cl, Br, CH3O, COOCH3, C6H5, CH3, and (CH3)3Sn) toward methanol has been investigated in the gas phase at 750 Torr and in the 40-120 degrees C temperature range and compared with that of IF (X = F) and ISi (X = (CH3)3Si) measured previously under similar conditions. Detailed analysis of the energy surface of the IMe (X = CH3) ion reveals that the activation barrier of its syn addition to methanol is significantly lower than that of the anti attack. In the 40-100 degrees C range, such a difference is strongly reduced by adverse entropic factors which are large enough to invert the IMe diastereoselectivity from syn to anti at T > 69 degrees C. The behavior of IMe diverges markedly from that of IF and ISi. Large adverse entropic factors account for the predominant syn diastereoselectivity observed in the reaction with IF (X = F), notwithstanding the anti enthalpy barrier is lower than the syn one. Adverse entropy plays a minor role in the reaction with ISi (X = (CH3)3Si) which instead exhibits a preferred anti diastereoselectivity governed by the activation enthalpies. Depending on the electronic properties of X, the kinetic behavior of the other IX ions obeys one of the above models. The gas-phase diastereoselectivity of IX ions responds to a subtle interplay between the sigma-hyperconjugative/electrostatic effects of the X substituent and the activation entropy terms. sigma-Hyperconjugation/field effects determine the pyramidal structure and the relative stability of the syn and anti conformers of IX as well as the relative stability of their addition transition structures and their position along the reaction coordinate. The diastereoselectivity of IX in the gas phase is compared with that measured in solution and with theoretical predictions.     

离子液体对H2O2氧化环己烯制备反-1,2-环己二醇的催化作用

以H2O2为氧化剂,研究了离子液体为催化剂和溶剂,环己烯氧化生成反-1,2-环己二醇的反应。 考察了不同咪唑型离子液体、反应时间、反应温度和H2O2用量等对产率和选择性的影响, 实验结果表明,在7种咪唑型离子液体催化体系中,阳离子为咪唑环上含有1或2个羧基,阴离子为[PF6]的离子液体催化效果较好。 反应温度为100 ℃,n(H2O2)∶n(Cyclohexene)＝1.1∶1,反应5 h时,离子液体c（0.60 g,2.1 mmol）催化生成的反-1,2-环己二醇的产率和选择性分别为95%和97%,而离子液体f（0.20 g,0.6 mmol）催化生成的反-1,2-环己二醇的产率和选择性分别为84%和90%,从离子液体的用量来看,含2个羧基的离子液体f的催化效率更高。     

采用醋酸钯/邻菲洛林/脂肪胺催化体系制备丙烯酸乙烯酯

以醋酸钯/邻菲洛林/脂肪胺为催化体系,丙烯酸和乙酸乙烯酯为原料,通过乙烯基交换反应制备丙烯酸乙烯酯。用红外光谱和核磁共振对产物的结构进行了分析和表征;用气相色谱研究了反应的产率;考察了不同种类的共催化剂、反应物配比、不同的脂肪胺对该反应体系催化活性和催化剂稳定性的影响。结果表明,加入脂肪胺能有效稳定钯催化剂,提高反应活性,反应产率达到60%以上。     

N,P掺杂型C@Mo_2C催化剂的制备及其催化CO_2加氢反应研究

以三聚氰胺苯甲酸盐为碳源和氮源、以三聚氰胺磷钼酸盐为钼源、磷源和氮源,采用程序升温的方法制备了系列N,P掺杂型C@Mo_2C催化剂。采用XRD、SEM、TEM和XPS等对催化剂的结构、形貌和表面特性进行了表征,研究了三聚氰胺苯甲酸盐中n(三聚氰胺)/n(苯甲酸)、前驱体中n(C)/n(Mo)等因素对所制备催化剂的结构及其在二氧化碳加氢反应中催化性能的影响。在反应温度为220℃、反应压力为3.0 MPa、空速为3 600 m L/(g·h)的条件下,在N,P掺杂型C@Mo_2C的催化作用下,CO_2转化率可以达到12.2%,此时产物中CH_3OH的选择性达到52.2%。     

Precipitation polymerization of 2‐hydroxyethyl methacrylate in supercritical carbon dioxide

We report the successful precipitation polymerization of 2‐hydroxyethyl methacrylate (HEMA) in supercritical carbon dioxide (scCO₂) at pressures ranging from 15 to 27 MPa utilizing 2, 2′‐azobisisobutyronitrile (AIBN) as a free radical initiator. The effects of the reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time were investigated. Analyses by scanning electron microscopy (SEM) indicated that in all reaction conditions, polymerization in the absence of stabilizer led to the formation of large aggregates of partially coalesced particles, with diameters of approximate 1–10 µm. Analyses by gel permeation chromatography (GPC) indicated that for the reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time studied there are appreciable effect on product molecular weight. Copyright © 2011 John Wiley & Sons, Ltd.     

Carbon-halogen bond activation mechanism by copper(I) complexes of (2-pyridyl)alkylamine ligands

The reaction of p-substituted benzyl halides ((Y)BnX; X = Cl, Br, and I; Y = p-substituent, OMe, t-Bu, Me, H, F, Cl, and NO(2)) and copper(I) complexes supported by a series of (2-pyridyl)alkylamine ligands has been investigated to shed light on the mechanism of copper(I) complex mediated carbon-halogen bond activation, including ligand effects on the redox reactivity of copper(I) complexes which are relevant to the chemistry. For both the tridentate ligand (Phe)L(Pym2) [N,N-bis(2-pyridylmethyl)-2-phenylethylamine] and tetradentate ligand TMPA [tris(2-pyridylmethyl)amine] complexes, the C-C coupling reaction of benzyl halides proceeded smoothly to give corresponding 1,2-diphenylethane derivatives and copper(II)-halide complex products. Kinetic analysis revealed that the reaction obeys second-order kinetics both on the copper complex and the substrate; rate = k[Cu](2)[(Y)BnX](2). A reaction mechanism involving a dinuclear copper(III)-halide organometallic intermediate is proposed, on the basis of the kinetic results, including observed electronic effects of p-substituents (Hammett plot) and the rate dependence on the BDE (bond dissociation energy) of the C-X bond, as well as the ligand effects.     

二氧化碳电催化还原中的电解质效应（英文）

二氧化碳(CO₂)电催化还原反应利用可再生能源将CO₂转化为高值燃料和化学品,是一种新型的碳中和技术。CO₂电催化还原反应在电极/电解质界面上进行,因此除催化剂以外,电解质对提高CO₂电催化还原反应性能同样至关重要。本文深度剖析了CO₂电催化还原反应中的电解质效应,结合近几年的最新研究进展,详细讨论了局部p H、阳离子、阴离子和离子交换膜等电解质组成和性质对电催化活性和产物选择性的影响,阐述了电解质效应的催化作用机制。本文特别强调了电化学原位红外/拉曼等振动光谱在电解质效应机理研究方面的优势以及面向实际应用的膜电极CO₂电解器中阴离子、阳离子、水、液体产物等物质传输对活性、选择性、能量效率及CO₂利用效率等关键催化性能指标的影响。本文最后提出了当前电解质效应研究中存在的挑战,并展望了未来的研究机遇和发展趋势。     

Direct sulfonation of methane to methanesulfonic acid with SO2 using Ca salts as promoters

Direct liquid-phase sulfonation of methane to methanesulfonic acid (MSA) with SO2 has been achieved in triflic acid using K2S2O8 as the oxidant and a small amount of a Ca salt as the promoter. The effects of reaction conditions on the conversion of SO2 to MSA were examined. Included were the influence of solvent acidity, reaction duration, reaction temperature, amount of K2S2O8, and composition and amount of promoters.     

二氧化碳和丙烯在Cu2(OEt)2/SiO2催化下超临界合成甲基丙烯酸

负载型双核金属乙氧基配合物催化剂Cu2(OEt)2／SiO2采用表面改性法制备。运用滴定、IR、DSC和超临界反应技术对催化剂的表面结构、化学吸附性质和反应性能进行了研究。结果表明：负载型双核金属乙氧基配合物Cu2(OEt)2／SiO2中Cu”与载体SiO2表面O^2-以双齿配位形式键合,存在Cu2(OEt)2双核结构;二氧化碳在催化剂表面吸附形式形成桥式和乙氧碳酸酯基物种两种吸附态,丙烯则只有一种分子吸附态;在超临界的反应条件下,二氧化碳和丙烯在Cu2(OEt)2／SiO2催化剂上可以高选择性地合成甲基丙烯酸;反应物分子共吸附于催化剂表面,同一活性基元以及羧酸根与丙烯解离吸附态的形成是反应顺利进行的关键因素。     

Quasiclassical trajectory study of reactive and dissociative processes in H2+H2: comparison with quantum-mechanical calculations

Quasiclassical trajectory calculations have been carried out for H(2)(v(1)=high)+H(2)(v(2)=low) collisions within a three degrees of freedom model where five different geometries of the colliding complex were considered. Within this approach, probabilities for different competitive processes are studied: four center reaction, collision induced dissociation, reactive dissociation, and three-body complex formation. The purpose is to compare in detail with equivalent quantum-mechanical wave packet calculations [Bartolomei et al., J. Chem. Phys 122, 064305 (2005)], especially the behavior of the probabilities near reaction thresholds. Quasiclassical calculations compare quite well with the quantum-mechanical ones for collision induced dissociation as well as for the four center reaction, although quantum effects become very important near thresholds, particularly for lower v(1)'s and for the four center process. Less quantitative agreement is found for reactive dissociation and three-body complex formation. It is found that most quantum effects are due to differences between quantum and classical vibrational distributions of H(2)(v(1)=high). Zero point energy violation has been found in the classical reactive-dissociative probabilities. Extension of these findings to full-dimensional treatments is examined.