单次碰撞条件下，反应Ba+C2H5Br、n-C3H7Br、1,2-C2H4Br2、1,3-C3H6Br2的动力学研究

Under single-collision beam-gas scattering conditions the reactions Ba+ C_2H, Br、n-C_3H_7Br、1, 2-C_2H_4Br_2、1,3-C_3H_6Br_2 have been studied using laser induced fluore-scence to detect the BaBr X~2∑~+ product. The vibrational distributions, the fractions of the available energy going into vibrational and rotational energy of the BaBr products have been calculated by means. of computer simulation. It has been found that the average vibrationel energies of the BaBr products can be described as a linear function of the mass factors for the reactions Ba+CH_3Br、C_2H_5Br、n-C_3H_7Br、1,3-C_3H_6Br, and that the potential energy surfaces for these reactions are similar. For the reactions Ba+CH_3Br、C_2H_5Br、n-C_3H_7Br, the vibrational increae, but for the reactions Ba+CH_2Br_2、1,2-C_2H_4Br_2、1,3-C_3H_6Br_2, the vibrational excitations of the BaBr products decrease greatly when the number of the carbons increase.     

Reactions of O+4 and O+2 with methane

Rate coefficients and products were determined for the title reactions employing a drift tube mass spectrometer apparatus. The implications of these reactions for the ion chemistry of the stratosphere is discussed.     

Reactions of thebaine with cis- and trans-disubstituted dienophiles

Thebaine has been shown to undergo Diels-Alder reactions with trans-disubstituted ethylenes containing relatively bulky groups. These were correlated with reactions in which the corresponding cis-disubstituted dienophiles were used. Reductions, Grignard reactions and base-catalyzed rearrangements of the adducts are described.     

Quantum chemistry study on the reactivity of PhOTiCl2CH2Cl and Cl3TiCH2Cl cyclopropanation reagents with olefins

In order to explore the new and efficient cyclopropanation reagents, a theoretical investigation of the cyclopropanation reactions of titanium carbenoid PhOTiCl₂CH₂Cl and Cl₃TiCH₂Cl with olefins was given at the B3LYP level of theory. All of the reactions examined displayed similar concerted mechanisms for the cyclopropanation of these reagents. The reactions are predicted to be highly chemical reactivity with low barriers and could be favored in experiment, and the cyclopropanation reaction proceed easily at lower temperature. The computational results are briefly compared to other carbenoid reactions and related species.     

Reversible Anionic Redox Activities in Conventional LiNi1/3Co1/3Mn1/3O2 Cathodes

Redox reactions of oxygen have been considered critical in controlling the electrochemical properties of lithium‐excessive layered‐oxide electrodes. However, conventional electrode materials without overlithiation remain the most practical. Typically, cationic redox reactions are believed to dominate the electrochemical processes in conventional electrodes. Herein, we show unambiguous evidence of reversible anionic redox reactions in LiNi_1/3Co_1/3Mn_1/3O₂. The typical involvement of oxygen through hybridization with transition metals is discussed, as well as the intrinsic oxygen redox process at high potentials, which is 75 % reversible during initial cycling and 63 % retained after 10 cycles. Our results clarify the reaction mechanism at high potentials in conventional layered electrodes involving both cationic and anionic reactions and indicate the potential of utilizing reversible oxygen redox reactions in conventional layered oxides for high‐capacity lithium‐ion batteries.     

Simultaneous propane dehydrogenation andco2hydrogenation overCrOx/SiO2catalyst

Summary Single reverse water-gas shift (RWGS) and dehydrogenation of propane with CO₂(DH-CO₂) reactions in the presence and absence of the CrO_x/SiO₂ catalyst have been studied between 673 and 873 K. It was found that the CrO_x/SiO₂ catalyst is active both in the dehydrogenation of propane and in the RWGS reactions. The obtained results suggest that the dehydrogenation of propane to propene in the presence of CO₂on CrO_x/SiO₂can be facilitated by the RWGS reaction.</o:p>     

Preparation, characterization and application of KNH2/Al2O3 and KF/Al2O3 as strong solid bases

This review describes the preparation, characterization and application of KNH₂ loaded on alumina and KF loaded on alumina. These strong solid bases catalyze a variety of organic reactions in a very selective manner. The reactions include isomerizations of alkenes and alkynes, dimerization of alkynes, Tishchenko reaction, and the reaction of silanes to form of Si–C, Si–N and Si–O bonds.     

Ca(1S0)+CH2Cl2、CHCl3和Ca(3P)+CH2Cl2、CHCl3反应的动态学研究

The reactions Ca(~1S_0)+ CH_2Cl_2, CHCl_3 and Ca(~3P)+ CH_2Cl_2, CHCl_3 were studied by means of the laser induced fluorescence (LIF). Systematic simulation of the observed LIF spectra revealed that change of the Ca atoms from the ~3p states to the ~1S_0 state brought about a decrease of the fraction of total energy going to the ground state CaCl product vibration and an increase of the fraction of total energy going to the ground state CaCl product rotation. Total cross sections for the reactions of Ca(~1S_0)+CH_(4-n)Cl_n(n=2, 3) and the fraction of the Ca atoms going to the ~3P states in the discharge Ca beam were estimated from the LIF indensity of the CaCl product and total cross sections for the reactions Ca(~3P)+CH_(4-n)Cl_n. They are 0.39±2 nm, 0.45±2 nm, 1.8+0.1%, respectively.     

Highly enantioselective aldol reactions using a tropos dibenz[c,e]azepine organocatalyst

The four-step synthesis of a chiral primary tertiary diamine salt, possessing a tropos dibenz[c,e]azepine ring is described. It is shown that 3.5-5 mol % of this salt is capable of promoting highly enantioselective crossed-aldol reactions between cyclohexanone and a series of aromatic aldehydes. In all cases, the aldol reactions proceed with high diastereoselectivity for the anti-aldol product. The outcome of crossed-aldol reactions involving other cyclic ketones and acyclic ketones are also described. All examples involving cyclic ketones result in selectivity for the anti-aldol products, whereas acyclic ketones were found to favour the syn-aldol products. A discussion on the role of the chiral primary tertiary diamine salt in the catalysis of the aldol reactions is also presented.     

Further links between the maximum hardness principle and the hard/soft acid/base principle: insights from hard/soft exchange reactions

Ayers, Parr, and Pearson recently showed that insight into the hard/soft acid/base (HSAB) principle could be obtained by analyzing the energy of reactions in hard/soft exchange reactions, i.e., reactions in which a soft acid replaces a hard acid or a soft base replaces a hard base [J. Chem. Phys., 2006, 124, 194107]. We show, in accord with the maximum hardness principle, that the hardness increases for favorable hard/soft exchange reactions and decreases when the HSAB principle indicates that hard/soft exchange reactions are unfavorable. This extends the previous work of the authors, which treated only the "double hard/soft exchange" reaction [P. K. Chattaraj and P. W. Ayers, J. Chem. Phys., 2005, 123, 086101]. We also discuss two different approaches to computing the hardness of molecules from the hardness of the composing fragments, and explain how the results differ. In the present context, it seems that the arithmetic mean of fragment softnesses is the preferable definition.     

Beam-gas chemiluminescent reactions of Cu(2D) with Cl2, Br2, and I2

Chemiluminescent reactions involving copper and halogen molecules are shown to result from the bimolecular reaction of metastable Cu(²D) with Cl₂, Br₂, and I₂ under single-collision conditions. The collision-energy dependence of the reactions is described by a hard-sphere model with zero threshold energy. Cross sections for these reactions are compared with that for chemiluminescent reaction of Cu(²S) with F₂.     

Reaction of iodobenzene dichloride with C5–C6 unsaturated steroids

Light and heat induced reactions of iodobenzene dichloride with 3β-substituted cholest-5-enes has been studied. The ratio of the isomeric 5,6-dichlorides formed was found to be nearly independent of the 3β-substituent. Radical mechanisms are proposed for these reactions. Chlorination of 3-iodocholest-5-enes may be complicated by side reactions in which iodine is liberated.     

Carbon nitride formation in gas-phase reactions of CH4, NH3 and H2: an ab initio study

Ab initio QCISD(T)/6-311++(2d,2p) calculations have been carried out for an extensive study of gas-phase reactions among CH₄, NH₃ and their radicals. Our study shows that stable HCN molecules are readily formed by successive H abstraction reactions. Some of the reactions are strongly exothermic and have negligible energy barriers. In agreement with some recent experiments, our results indicate that H abstraction reactions, which make the chemical vapor deposition of diamond thin films successful, do not favor the formation of carbon nitride thin films.     

Reduction of beta-hydroxyketones by SmI2/H2O/Et3N

Reduction of a series of beta-hydroxyketones by SmI2/H2O/Et3N provided 1,3-diols in quantitative yields. The reactions were exceedingly clean with no byproduct formation, negating the need for further purification. Most reactions provided moderate to excellent diastereoselectivity with syn-diols as the major isomer in most instances.     

Microwave-assisted SNAr reaction of 2,4,6-trichloro-1,3,5-triazine for the rapid synthesis of C3-symmetrical polycarboxylate ligands

The microwave-assisted S_NAr reaction of 2,4,6-trichloro-1,3,5-triazine with various unprotected amino acids was developed for the synthesis of C₃-symmetrical polycarboxylate ligands which can be used as structural directing units in metal-organic frameworks. The reactions were performed in water using a domestic microwave oven as the heating device. In comparison to the reactions performed under conventional heating, the reactions under microwave irradiation proceeded much more rapidly within 20 min to afford the desired ligands in comparative yields to those obtained by conventional heating.     

One electron C-C bond forming reactions VIA allylstannanes: Scope and limitations

Free radical (or “one-electron”) methodology for carbon-carbon bond forming reactions using allylstannanes is described in detail. Such reactions have the advantages of tolerating quite complex functionality in the substrate and of being nearly stoichiometric in reagents, and not requiring extensive experimentation for application to new substrates.     

Characterization of a DAPI-RIT-DAPI System for Gas-Phase Ion/Molecule and Ion/Ion Reactions

The discontinuous atmospheric pressure interface (DAPI) has been developed as a facile means for efficiently introducing ions generated at atmospheric pressure to an ion trap in vacuum [e.g., a rectilinear ion trap (RIT)] for mass analysis. Introduction of multiple beams of ions or neutral species through two DAPIs into a single RIT has been previously demonstrated. In this study, a home-built instrument with a DAPI-RIT-DAPI configuration has been characterized for the study of gas-phase ion/molecule and ion/ion reactions. The reaction species, including ions or neutrals, can be introduced from both ends of the RIT through the two DAPIs without complicated ion optics or differential pumping stages. The primary reactant ions were isolated prior to reaction and the product ions were mass analyzed after controlled reaction time period. Ion/molecule reactions involving peptide radical ions and proton-transfer ion/ion reactions have been carried out using this instrument. The gas dynamic effect due to the DAPI operation on internal energy deposition and the reactivity of peptide radical ions has been characterized. The DAPI-RIT-DAPI system also has a unique feature for allowing the ion reactions to be carried out at significantly elevated pressures (in 10^–1 Torr range), which has been found to be helpful to speed up the reactions. The viability and flexibility of the DAPI-RIT-DAPI system for the study of gas-phase ion reactions have been demonstrated.

The stereoselective synthesis of highly functionalized tertiary 3-aminoindoles/anilines or dihydropyrroles from C-(3-indolyl)-N-aryl and C,N-diaryl nitrones

We report on the novel properties of nitrones including their transformations via reactions with sodium malonates to give functionalized stereodefined derivatives of tertiary 3-aminoindoles or anilines, as well as fully-substituted dihydropyrroles. The outcome of the reactions is dependent mainly upon the nature of the starting C-nitrone substituent and solvent used. The formation of a new carbon-nitrogen bond in the obtained amines occurs via a nucleophilic 1,2-aryl/3-indolyl shift from C to the adjacent nitrogen.     

Sequential Pd/Ru-catalysed allenylation/olefin metathesis/1,3-dipolar cycloaddition route to novel heterocycles

A novel sequential palladium/ruthenium-catalysed four component process is described involving carbonylation of an aryl/heteroaryl iodide followed by allenylation to generate (π-allyl) palladium species which are intercepted by nitrogen nucleophiles to afford 1,6-dienes. Subsequent Ring-Closing Metathesis (RCM) affords C-acyl-N-heterocycles in good yield. These heterocycles proved to be active dipolarophiles in sequential and cascade 1,3-dipolar cycloaddition reactions (1,3-DC) as exemplified by reactions with nitrones and azomethine ylides.     

Ni催化的碳(sp2)-碳和碳(sp2)-杂交叉偶联反应

综述了Ni催化的碳(sp²)-碳和碳(sp²)-杂交叉偶联反应. 主要反应类型有: Heck反应、Sonogashira反应、Kumada-Corriu反应、Negishi反应、Stille反应、Suzuki反应、Ullmann反应、C—N偶联反应、C—O偶联反应、C—P偶联反应和C—S偶联反应. 详细地介绍了各个反应的底物要求、反应条件、反应选择性和产率. 最后, 我们对Ni催化的反应机理研究也作了总结.