1-甲基-3,5-二苯基吡唑啉在氯化铜催化下的氧化脱氢反应(Ⅱ)——计量反应与氧分子的作用阶段

我们在合成1-甲基-3,5-二苯基吡唑(MDPP)的过程中,发现氯化铜、氯化钴等化合物对1-甲基-3,5-二苯基吡唑啉(H₂MDPP)的氧化脱氢反应具有优异的催化性能,对以氯化铜为催化剂的反应机理进行了初步研究,获得了反应过程中形成铜(Ⅱ)H₂MDPP、铜(Ⅱ)MDPP和铜(Ⅱ)H₂MDPP分子氧配合物的证据。另外,在催化氧化反应体系中曾检测到一价铜,这显然是氯化铜的还原产物,故本文对氯化铜与H₂MDPP的计量反应及在催化反应中氧分子参与作用的阶段进行了研究。     

Kinetic study of Berthelot reaction steps in the absence and presence of coupling reagents

Several reaction steps in the Berthelot reaction for the determination of ammonia have been separately studied. A reaction order of two has been confirmed for the reaction between HOCl and NH(3). The rate constant for this reaction has been determined to be 3.2 x 10(6)l.mole(-1).sec(-1). The first evidence for the formation of benzoquinonechlorimine is presented. Pentacyanoferrate coupling reagents which accelerate the production of indophenol have been found to operate on the reaction between NH(2)Cl and phenol. The rate constant for the final step of the reaction sequence has been determined to be 5.3 x 10(-3)l.mole(-1).sec(-1). A reaction between chlorimine and pentacyanoferrate compounds has been found to be responsible for the formation of a green product in the presence of excess of coupling reagent.     

硅烯与乙烯环加成反应的理论研究

用从头计算方法研究了单重态硅烯与乙烯的环加成反应，得到了此反应可行的反应机理．并用统计热力学方法和过渡态理论计算了该反应的热力学函数和动力学性质．     

聚乙二醇催化下的反常Reimer—Tiemann反应

自1876年Reimer-Tiemann反应(以下简称R-T反应)提出后,许多化学工作者曾对该反应进行了深入研究。1988年丁新腾等又报道了叔胺存在下的反常R-T反应。但以聚乙二醇(PEG)为相转移催化剂,催化R-T反应未见报道。本文报道了无水相存在下PEG催化的反常R-T反应,并对其催化行为从理论上进行了探讨。     

Radical polymerization as an indicator reaction for determination of organic compounds

Polymerization of methyl methacrylate (MMA) and 4-vinylpyridine (VP) has been carried out in an aqueous solution in the presence of the initiating system persulfate-tetramethylethylenediamine. The reaction rate has been monitored by measuring the light absorbance of the suspension of the resulting polymer. The effect of 26 model organic compounds on the polymerization rate has been studied. It has been shown that the VP polymerization is inhibited by a smaller number compounds (9 compounds) than the MMA polymerization (22 compounds), which indicates that the former reaction has better selectivity, whereas the determination of model compounds using the MMA polymerization reaction is more sensitive. This is explained by the lower chain growth rate constant for VP vs. MMA and different stationary concentrations of radicals in the systems. The use of these indicator polymerization reactions makes it possible to distinguish some closely related compounds, e.g., 1,4-benzoquinone and 9,10-anthraquinone (MMA reaction) or dinitrophenol and 4-nitrophenol or phenol (VP reaction). Determination of ascorbic acid in a pharmaceutical formulation has been carried out.     

An investigation of the Lewis acid mediated 1,3-dipolar cycloaddition between N-benzyl-C-(2-pyridyl)nitrone and allylic alcohol. Direct entry to isoxazolidinyl C-nucleosides

The cycloaddition reaction of N-benzyl C-(2-pyridyl) nitrone with allylic alcohol has been carried out to obtain the corresponding 2-benzyl-3-(2-pyridyl)-5-hydroxymethylisoxazolidine. The influence of Lewis acids in the reaction has been studied and a complete 3,5-regioselectivity and cis diastereoselectivity was observed when the reaction was carried out with 1.0 equiv of AgOTf, [Ag(OClO3)(PPh2Me)] or Zn(OTf)2. Insight into the mechanism of the reaction has been obtained by isolating and characterizing (X-ray) the intermediate complexes. Also, a model based on both experimental and theoretical results is proposed.     

Exact quantum and TST-CEQ study of the collinear reaction O+HCl

Exact quantum calculations of reaction probabilities have been carried out using hyperspherical coordinates for the collinearr reaction O+HCl(v <1) -OH(v'<1)+Cl . A generalized LEPS potential energy surface with a barrier height of 8.12 kcal/mol has been used in the calculations. According to the calculated results we found that (1) the reaction probability oscillates with energy, (2) the reaction probability shows vibrational adiabaticity, although it is poorer than that for symmetric reaction Cl + HC1. The analysis of resonance has also been done. The reaction rate constants and average cross sections have been calculated by TST-CEQ method. The rate constants are in agreement with that by QCT and smaller than the experimental one. Finally, the threshold has been estimated and is in good agreement with that of the literature.     

Transformation of 1,1-Dichloro-2,2-bis(4-nitrophenyl)ethene in the Reaction with Nitrite Ion in Polar Aprotic Solvents

The reaction of 1,1-dichloro-2,2-bis(4-nitrophenyl)ethene with sodium nitrite in polar aprotic solvents has been studied. Products of the reaction have been identified, and effects of different factors, including reactant dissociation and solvation, on the reaction rate constants have been analyzed. Thermodynamic parameters of the reaction have been determined, the multistep process has been simulated by quantum chemical calculations, and a plausible mechanism has been proposed.     

VDF/CTFE共聚物原子转移自由基反应法氢化制备VDF/TrFE/CTFE三元共聚物的研究

报道了一种用于偏氟乙烯-三氟氯乙烯共聚物(VDF/CTFE共聚物)制备偏氟乙烯/三氟乙烯/三氟氯乙烯共聚物(VDF/TrFE/CTFE共聚物)的新方法,该方法以CuCl与2′,2-Bpy的配合物为催化剂,N-甲基吡咯烷酮(NMP)为溶剂,异丙苯(丙酮、2,6-二叔丁基-4-甲基苯酚)为链转移剂,通过原子转移法在VDF/CTFE共聚物上产生自由基,进而利用自由基链转移反应将VDF/CTFE共聚物上部分Cl原子用H原子取代以制备VDF/TrFE/CTFE三元共聚物.对该体系的反应机理及其影响因素进行研究发现,随着实验温度的升高(80～140℃),反应时间的延长,氢化量增加,产物中TrFE含量增加;反应温度越高,初始反应速度越快,完全氢化时间越短;催化剂与氢化量的比例基本为1:1,通过控制催化剂的量可以定量控制氢化率;新的反应体系不会对产物的分子量产生大的影响.     

A spectrophotometric study of the determination of gold with phenothiazine

The reaction of Au(III) with phenothiazine has been studied and a reaction mechanism proposed. Optimal conditions for the reaction have been found and a new spectrophotometric method has been developed for determination of Au(III). The method is advantageous in its simplicity and reproducibility. Gold can be determined in the concentration range 2-20 mug/ml.     

The nature of the surface species formed on Au/TiO2 during the reaction of H2 and O2: an inelastic neutron scattering study

Inelastic neutron spectroscopy (INS) has been employed to identify surface species formed during the H2-O2 reaction on Au/TiO2 catalysts. Determination of the surface intermediates formed in this reaction is crucial to develop a mechanistic understanding for the direct vapor-phase propylene epoxidation reaction and synthesis of H2O2. Although the presence of intermediate hydroperoxo species (during these reactions) has been suggested in literature, it has never been demonstrated. Our studies provide direct evidence for the formation of surface hydroperoxo species during the H2-O2 reaction.     

Tripodal borate ligands from tris(dimethylamino)borane: the first synthesis of a chiral tris(methimazolyl)borate ligand, and the crystal structure of a single diastereomer pseudo-C3-symmetric Ru(II) complex

The activation of tris(dimethylamino)borane towards reaction with a chiral methimazole by N-methylimidazole has been used to prepare the first example of a chiral tris(methimazolyl)borate ligand. Coordination of this neutral ligand to Ru(II) has been achieved by reaction with [(p-cymene)RuCl(2)](2) to provide a single diastereomer complex in which the chirality of the methimazolyl substituents dictate the chirality of the bicyclo[3.3.3]cage formed by the ligand on coordination to the metal. The alternative approach to chiral tris(methimazolyl)borate ligands involving the introduction of a chiral group onto the boron atom has been explored by replacing N-methylimidazole in the above reaction by chiral oxazolines as activating bases in reaction with simple methimazole. However, although the B(NMe(2))(3) is activated to reaction with methimazole by these oxazolines, an intramolecular oxazoline ring-opening by a coordinated methimazolyl sulfur occurs and prevents the successful synthesis of these ligands.     

Enantioselective one-pot three-component synthesis of propargylamines

[reaction: see text] A copper(I) complex of i-Pr-pybox-diPh has been found to be an efficient catalyst for an enantioselective one-pot three-component synthesis of propargylamines from aldehydes, amines, and alkynes. The reaction has been applied to a wide variety of aromatic aldehydes with excellent yields (up to 99%) and enantiomeric excesses (up to 99% ee). A transition-state model has been proposed to explain the stereochemical outcome of the reaction.     

A highly enantioselective hetero-Diels-Alder reaction of aldehydes with Danishefsky's diene catalyzed by chiral titanium(IV) 5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol complexes

The catalytic effect of chiral Lewis acids on the hetero-Diels-Alder reaction between aldehydes and Danishefsky's diene (1) has been investigated. A variety of combinations of different ligands and Lewis acids have been examined as catalysts for the hetero-Diels-Alder reaction between benzaldehyde and 1, and it has been found that the readily accessible Ti(IV)-H(8)-BINOL (TiHBOL) complex is a very effective catalyst for the reaction, leading to products with very high enantioselectivity (up to 99% ee) and yield (92%). The hetero-Diels-Alder reaction of other aldehydes with 1 under the catalysis of TiHBOL is a general reaction which proceeds well with very high enantioselectivity and isolated yield for various aldehydes at 0 degrees C to room temperature. Based on the experimental results, the proposed mechanism of the hetero-Diels-Alder reaction and the dihedral angle effects of ligands are discussed.     

Metal exchange reaction of magnesium octaphenyltetraazaporphyrin with copper,cobalt, and zinc chlorides in DMSO and DMF

Metal exchange reaction of (octaphenyltetraazaporphyrinato)magnesium(II) with copper, cobalt, and zinc chlorides in dimethyl sulfoxide and dimethylformamide has been studied by spectrophotometry. Kinetic and thermodynamic parameters of the process have been determined, and a probable reaction mechanism has been proposed. Zinc(II), copper(II), cobalt(II), and cobalt(III) complexes of octaphenyltetraazaporphyrin have been isolated and characterized.     

铁(III)催化多卤代变色酸双偶氮胂类试剂的褪色反应特性及其应用

本文研究了铁(III)催化H2O2还原多卤代变色酸双偶氮胂类试剂(PHA)的褪色反应动力学行为, 测定了反应级数和反应活化能, 获得了经验速率方程, 探讨了反应机理, 稳态处理后的动力学方程与经验速率方程相吻合, 说明了机理的合理性。并以三氯偶氮胂为指示反应试剂, 测定了人发中痕量铁的含量, 得到了满意的结果。     

Magnesium(II) and cadmium(II) octaphenyltetraazaporphyrinates in metal exchange reaction with MnCl<Subscript>2</Subscript> in DMSO

Reaction kinetics of metal exchange of Mg(II) and Cd(II) octaphenyltetraazaporphynates with MnCl₂ in DMSO has been studied by spectrophotometry. Kinetic parameters of the metal exchange reaction have been determined. Possible stoichiometric reaction mechanism has been suggested. Effect of solvent and salt solvate nature on the rate of metal exchange reaction has been revealed.     

The initiation of polymerization by organometallic compounds—V. The termination mechanism in the polymerization of acrylonitrile initiated by tetrakis(dimethylamido)titanium(IV)

A simple method is described for the preparation of pure, dry alcohols, tritiated in the hydroxyl group. The polymerization of acrylonitrile initiated by tetrakis(dimethylamido)titanium(IV) has been terminated by quenching with tritiated isopropanol at varying reaction times, and the radioactivity of the polymer has been determined, in order to measure the concentration of metal-polymer bonds present in the reaction. The results indicate that about 97 per cent of the polymer present has been terminated by a reaction leading to detachment of the polymer chain from the metal centre. A very small fraction of the total polymer is terminated by a reaction which does not lead to detachment of the polymer. Possible reaction mechanisms are discussed.     

Practical highly enantioselective synthesis of propargylamines through a copper-catalyzed one-pot three-component condensation reaction

The one-pot three-component reaction of terminal alkynes, aldehydes and secondary amines in the presence of copper(I) bromide/quinap is reported. The reaction scope has been determined and a broad variety of all three components has been used, which afforded the corresponding propargylamines in good to excellent yields and moderate to very good enantioselectivities. The reaction showed a strong positive nonlinear effect. The transformation of a propargylamine intermediate into the alkaloid (S)-(+)-coniine has also been described.     

A unified mechanistic view on the Morita-Baylis-Hillman reaction: computational and experimental investigations

The thermodynamic properties and reaction mechanism of the Morita-Baylis-Hillman (MBH) reaction have been investigated through experimental and computational techniques. The impossibility to accelerate this synthetically valuable transformation by increasing the reaction temperature has been rationalized by variable-temperature experiments and MP2 theoretical calculations of the reaction thermodynamics. An increase in temperature results in a switching of the equilibrium to the reactants occurring at even moderate temperature levels. The complex reaction mechanism for the MBH reaction has been investigated through an in-depth analysis of the suggested alternative pathways, using the M06-2X computational method. The results provided by this theoretical approach are in agreement with all the experimental/kinetic evidence such as reaction order, acceleration by protic species (methanol, phenol), and autocatalysis. In particular, the existing controversy about the character of the key proton transfer in the MBH reaction (Aggarwal versus McQuade pathways) has been resolved. Depending on the specific reaction conditions both suggested pathways are competing mechanisms, and depending on the amount of protic species and the reaction progress (early or late stage) either of the two mechanisms will be favored.