混合多卤甲烷与金属镁反应产生溴氯卡宾及其反应机理的研究

应用CHBr3/CHCl3或CHBr3/CCl4和金属镁在一般的Grignard反应条件下与烯烃反应, 制备偕溴氯环丙烷衍生物。该反应原料易得, 反应条件温和, 产率良好, 后处理方便, 是制备偕溴氯环丙烷衍生物的一种简便的新方法。文中研究了上述反应的单电子转移和自由基链循环的复杂反应机理。     

A new ketone synthesis by palladium-catalyzed cross-coupling reactions of esters with organoboron compounds

[reaction: see text] The palladium-catalyzed coupling reaction of 2-pyridyl esters with organoboron compounds is described. The reaction is compatible with various functional groups and proceeds under mild reaction conditions. The coordination of the nitrogen atom to Pd is a key step for efficient reaction.     

Effect of Cationic Micelle on the Kinetics of Oxidation of Citric Acid by N-Bromophthalimide in Acidic Medium

Kinetics of the oxidation of citric acid (CA) by N-bromophthalimide (NBP) has been studied in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) at 35°C. The CMC value is lower than those given in the literature for aqueous solutions of CTAB without added electrolyte. The reaction is strongly catalyzed by cationic micelle, CTAB with a progressive increase in CTAB concentration the reaction rate increased, at higher concentration constancy in the rate constant was observed. The reaction follows first and fractional order kinetics in NBP and citric acid, respectively. The reaction follows inverse fractional order with respect to perchloric acid. The Arrhenius equation is found to be valid for the reaction. A detailed mechanism with the associated reaction kinetics is discussed. The catalytic role of CTAB micelles is discussed in terms of the Menger and Portnoy model.     

Transition-metal-free Suzuki-type coupling reactions: scope and limitations of the methodology

The scope and limitations of the transition-metal-free Suzuki-type coupling of aryl halides and arylboronic acids to form biaryls are presented. Confirmation that the reaction is indeed metal-free is presented. The effects of changing base, solvent, reaction temperature, phase-transfer catalyst, and substrate are shown and the implications of these results discussed in terms of their impact on the synthetic versatility of the methodology. The main findings are that the reaction works well for aryl bromides, water is necessary as a solvent for the reaction, the optimum temperature for the reaction is 150 degrees C, the reaction is best performed by using microwave promotion with the exception of an electron-poor aryl bromide example where conventional heating may be used, only limited boronic acids can be used as coupling partners, sodium carbonate is the best base for the reaction, tetrabutylammonium bromide proves to be the best phase-transfer catalyst for the reaction, the reaction is limited to couplings between aryl halides and aryl boronic acids with sp(2)-sp(3) couplings proving ineffective, and NaBPh(4) can be used in the place of phenylboronic acid as a phenylating agent.     

Kinetics of phenol oxidation with ozone in a thin layer on a solid surface

Ozone has been reacted with phenol in thin supported layers, and the dynamics of this reaction has been investigated. The stoichiometry of this reaction coincides with the stoichiometry of the same reaction in solution. Specific reaction rate (β) has been determined for various phenol conversions. The effective rate constant of the reaction, estimated by extrapolating β to zero reaction time, is significantly higher than the rate constant of the reaction in solution. The reaction between ozone and phenol is diffusion-controlled. The reaction products form a barrier layer, which protects the deeper phenol layers against ozone. The barrier layer is as thick as 8–15 phenol monolayers.     

Interaction of dimethyl carbonate with anilines in the presence of potassium methylate: Kinetics and the role of the base

The kinetic patterns of the reaction between dimethyl carbonate and anilines in the presence of a potassium methylate as a catalyst were studied. The mechanism of aminolysis was clarified, which includes the detachment of the proton from the amino group of aniline and the subsequent attack of the resulting anion on the carbonyl group of dimethyl carbonate. It is shown that when the reaction occurs in the dimethyl carbonate-methanol 3:1 system, the process can be described as an irreversible first-order reaction in the aniline though the target reaction is complicated by side interaction between potassium methylate and dimethyl carbonate. The rate constants of the target reaction with substituted anilines and of the side reaction in the temperature range of 70-90°C were determined. It is shown that the influence of the substituent on the reaction rate is described by the Hammett equation, with the constant of the reaction series being positive and the best correlation being achieved for σ-scale. The results obtained are consistent with the proposed mechanism of the reaction and are explained by the facilitation of the aniline deprotonation with increasing acceptor properties of the substituent. Effective activation energies for the reaction of various anilines with dimethyl carbonate are found.     

The reaction of porphyrins with organolithium reagents

Porphyrins react readily with organolithium reagents, preferentially in the meso positions. The overall reaction is a nucleophilic substitution and proceeds via initial reaction of the organic nucleophile with a meso carbon yielding an anionic species which is hydrolyzed to a porphodimethene (5,15-dihydroporphyrin), formally constituting an addition reaction to two Cm positions. Subsequent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) yields meso-substituted porphyrins. The reaction is highly versatile as it is accomplished in high, often quantitative yields with various alkyl or aryl lithium reagents. In addition, LiR can be used for reaction with a variety of metal complexes (best with NiII, but also with ZnII, CuII, and CoII) and most useful with free base porphyrins. Similarly beneficial this reaction can be used in sequence for the introduction of 1, 2, 3, or 4 (different) meso substituents giving for the first time an entry into any desired meso-substituted porphyrin. If meso-substituted porphyrins are used, reaction with LiR can be used for either the preparation of phlorins (already known reaction), porphodimethenes (5,15-dihydroporphyrins, including those with exocyclic double bonds, for example, 5(1),5(2)-didehydroporphyrins) or chlorins (2,3-dihydroporphyrins) depending on the substituent type in the reactant porphyrins. Thus, this reaction presents a generally applicable method for the facile and versatile functionalization of porphyrins.     

Mathematical modeling of cyclic voltammetry for EC reaction

The non-steady-state concentration for an EC reaction at planar electrode is derived. The analytical expression for the concentration for EC reaction is reported for small and large value of reaction rate. The asymptotic expression for the non-steady-state current for EC reaction is also derived. The analytical solutions for normalized current response were formulated using the method of Laplace transformation. The concentration and current are compared with available limiting case results, and are found to be in good agreement.     

Theoretical studies of metallo (Li and Na)-ene reaction mechanisms

The reaction mechanisms of allyl-lithium and allyl-sodium with ethylene were studied by ab initio molecular orbital (MO) methods. The reaction mechanisms were analyzed by a CiLC-IRC method on the basis of ab initio CASSCF MOs. The ene reaction pathways of allyl-Li and allyl-Na with ethylene were located. The complex between allyl-metal and ethylene for both systems is found in the first step of the reaction, and then the metal migration and new C-C bond formation occur synchronously through the transition state. The complexation energies are -13.2 and -9.6 kcal/mol for Li and Na systems, respectively. The activation energy barriers from the reactants are 3.5 kcal/mol for the Li system and 2.0 kcal/mol for the Na system at the MRMP2 calculation level. These barriers are significantly lower than that of the ene reaction of propene with ethylene as the parent reaction. The CiLC-IRC analysis shows that the reaction of allyl-metal with ethylene is a concerted ene reaction mechanism, not a metal catalysis and/or a stepwise reaction.     

Effect of amine nature on reaction mechanism: aminolyses of o-4-nitrophenyl thionobenzoate with primary and secondary amines

Pseudo-first-order rate constants (k(obs)) have been measured spectrophotometrically for reactions of O-4-nitrophenyl thionobenzoate (2) with a series of primary and acyclic secondary amines. The plots of k(obs) vs amine concentration are linear for the reaction of 2 with primary amines. The slope of the Br?nsted-type plot for the reaction of 2 with primary amines decreases from 0.77 to 0.17 as the amine basicity increases, indicating that the reaction proceeds through a zwitterionic addition intermediate in which the rate-determining step changes from the breakdown of the intermediate to the reaction products to the formation of the intermediate as the amine basicity increases. On the other hand, for reactions with all the acyclic secondary amines studied, the plot of k(obs) vs amine concentration exhibits an upward curvature, suggesting that the reaction proceeds through two intermediates, e.g., a zwitterionic addition intermediate and an anionic intermediate. The microscopic rate constants (k(1), k(-)(1), k(2), and k(3) where available) have been determined for the reactions of 2 with all the primary and secondary amines studied. The k(1) value is larger for the reaction with the primary amine than for the reaction with the isobasic acyclic secondary amines, while the k(-)(1) value is much larger for the latter reaction than for the former reaction. The k(3) value for the reaction with secondary amine is independent of the amine basicity. The small k(2)/k(-)(1) ratio is proposed to be responsible for the deprotonation process observed in aminolyses of carbonyl or thiocarbonyl derivatives.     

异丁烯直接胺化合成叔丁胺反应的热力学研究

叔丁胺是一种重要的有机化工中间体,广泛应用于制备橡胶促进剂,医药,农药,着色剂等诸多下游产物.目前,叔丁胺主要的生产方法,如叔丁脲水解法,异丁烯-氢氰酸法(Ritter法),卤代烃胺化法等存在产品收率较低,涉及强酸/强碱的使用,对设备腐蚀和环境污染严重等问题.异丁烯直接胺化生产叔丁胺,原子利用率100%,是典型的绿色化学反应.20世纪末,BASF公司以β沸石为催化剂,率先实现了异丁烯胺化技术的工业应用.但是,其反应条件苛刻,压力达28 MPa,生产过程能耗大,对设备材质要求高.目前,关于异丁烯直接胺化的文献较少,且相关研究多在远离工业应用的常压条件下进行.同时,对于异丁烯直接胺化反应过程的热力学,特别是缓和反应条件下的热力学尚待进一步系统和深入地研究分析,以期指导低温低压条件下高性能胺化催化剂的研发和工艺条件优化.我们计算了473?573 K间,异丁烯胺化制备叔丁胺反应的ΔrH,ΔrG,Kp等热力学数据.在此基础上,分析了反应温度,压力和氨烯比(摩尔比)对异丁烯平衡转化率(叔丁胺选择性>99%,未予考虑)的影响.结果表明,异丁烯胺化是中等强度的放热反应,升高反应温度会急剧降低异丁烯的平衡转化率,如在5 MPa,氨烯比1的条件下,反应温度从473 K提高到573 K,异丁烯平衡转化率从40.6%降到6.9%.但从动力学角度而言,升温可提高胺化反应速率,因此在特定的反应条件下和催化剂上,必然存在最佳反应温度.提高反应压力和氨烯比有利于提高异丁烯的热力学平衡转化率.开发在低温和相对较低的压力下具有较高胺化活性的催化剂是提高该过程经济性和实用性的关键.在较缓和的反应条件下(523 K,5 MPa,氨烯比4及异丁烯空速0.5 h?1),考察了ZSM-5(R=50和R=412,R为硅铝比,下同),ZSM-11(R=48),MOR(R=10),SAPO-11(摩尔组成,1.6Al2O3:1.0SiO2:1.4P2O5)等不同拓扑结构分子筛以及氧化铝在异丁烯胺化反应中的性能.结果表明,空白试验中,无叔丁胺产物生成.在ZSM-11上的获得最高的异丁烯胺化转化率,为14.2%(达到平衡转化率的52.2%),在ZSM-5(R=50),ZSM-5(R=412)和MOR上,异丁烯转化率分别为13.9%,6.4%和2.9%,叔丁胺选择性均大于99.8%.而SAPO-11和氧化铝未呈现出胺化反应活性.关联氨气程序升温脱附,吡啶吸附红外表征结果及分子筛孔结构特点,表明分子筛胺化活性与其孔径及Br?nsted酸的酸量和酸强度密切相关.为了进一步验证实际反应体系中反应条件对异丁烯胺化反应过程的影响规律,我们在ZSM-11催化剂上,系统考察了反应温度,压力,氨烯比和异丁烯空速对催化剂胺化反应性能的影响及变化规律.结果表明,在其他条件不变的情况下,异丁烯转化率随着温度的升高呈现出先增大后减小的趋势.适当提高原料中氨烯比和反应压力,以及采用较低异丁烯空速有利于促进异丁烯的转化.上述规律与热力学计算结果呈现出较好的一致性.在ZSM-11催化剂上,异丁烯直接胺化反应的较佳反应条件为523 K,5 MPa,氨烯比4,异丁烯空速0.5 h?1.上述结果可为异丁烯直接胺化合成叔丁胺过程新型高效催化剂的研发和反应工艺条件优化提供参考和指导.     

Kinetics and mechanism of the additive reaction of aniline with dicyandiamide

Kinetics of the additive reaction of aniline with dicyandiamide resulting in phenylbiguanide production was studied based on the analysis of reaction rate by high performance liquid chromatography. It is a second-order reaction on the condition of the constant temperature and acidity. It is first-order for both aniline and dicyandiamide. The reaction rate is influenced evidently by acidity. It reaches its maximum at pH 2.6. The mechanism for this reaction was suggested that aniline is nucleophilic reagents additive with the protonated cyano-group in dicyandiamide. The rate equation derived from the mechanism can describe the experimental results well. The reaction rate calculated from the rate equation reaches its maximum at pH 2.5, which is close to the experimental result. For different aromatic amine adding to dicyandiamide have the same reaction order, the mechanism ought to be the same. Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 3, pp. 379–385. The article is published in the original.     

Kinetics of the post-column complexation reaction of Cu(II) with N-formylmethionyl chemoattractant and chemotactic peptides

The N-formylmethionyl peptides comprise an important class of peptides that activate neutrophils to attack microbial invaders. The post-column reaction of Cu(II) with peptides following their separation leads to electroactive complexes that are detectable with electrochemical detection. The need to minimize post-column band spreading puts constraints on the time allowed for the complexation reaction to occur. For most peptides, the reaction rate is rapid, however, for peptides without a free terminal amine the reaction rate is slower. In order for this detection scheme to be sensitive to so-called N-blocked peptides, the rate law and the influence of buffers need to be understood.The kinetics of the complexation of Cu(II) with several N-blocked chemoattractant and chemotactic peptides are similar. One N-blocked peptide, N-f-MLF, has been studied in detail. Two parallel paths have been found for the complexation reaction. The reaction at the amide terminus is first order in [peptide] and [OH(-)]. The reaction at the carboxylate terminus is first order in [peptide], [Cu(II)], and total carbonate at constant pH. The response of the rate as pH is changed reveals that bicarbonate ion is the active species.     

Investigation of reaction products of sulphuric acid with ilmenite

The reaction of sulphuric acid with titanium raw materials runs violently with simultaneous emission of gases. Such run of reaction creates danger of explosion. This process is very complicated from the reason of complexity of reactions and variety of compounds in reaction mixture. To determine safe conditions of reaction with high efficiency, it is necessary to investigate phase composition products of reaction. Products of reaction were investigated by using X-ray diffraction. However reaction products show high amorphy and this is the reason of difficulties to determine all phases. For this reason also was used additional method — ‘drop’ calorimeter. This method is used for determination of average specific heat of liquid or solid samples. In this case, this method was used for verification of phase composition of products of reaction. On the basis of investigation the phase composition of reaction product is following: titanyl sulfate, iron(III) sulfate, monohydrated iron(II) sulfate, magnesium sulfate and unreacted remainders of ilmenite and magnesium silicate.     

湿法脱硫中亚硫酸盐非催化氧化本征动力学

亚硫酸盐的氧化是湿法烟气脱硫工艺中的重要过程. 利用间歇式反应装置, 研究了亚硫酸盐非催化氧化的本征反应动力学. 结果表明, 该反应分为两个阶段进行, 即富氧区的快速反应和贫氧区的慢速反应. 在富氧区, 亚硫酸盐和溶解氧的分级数分别为1.0和1.0, 反应的表观活化能为49.3 kJ•mol^－1; 在贫氧区, 亚硫酸盐和溶解氧的分级数分别为2.0和0, 反应的表观活化能为122.6 kJ•mol^－1. 对反应的机理进行了预测, 结果与实验现象有较好的吻合.     

固体聚合物电解质在肉桂醇电解氧化中的应用(II)——后续化学反应在电催化反应中的地位及其影响因素

对影响肉桂醇电极氧化的各种因素作了进一步的讨论. 实验结果表明固体聚合物电解质内水的含量、pH 以及浸入离子交换膜中的二价锰离子的浓度均对该电极反应的电位以及后续化学反应的速度有很大的影响, 在较高的温度下反应时, 有利手提高生成肉桂醛的电流效率.     

Theoretical analysis of concerted and stepwise mechanisms of the hetero-Diels–Alder reaction of butadiene with formaldehyde and thioformaldehyde

The concerted and stepwise mechanisms of the hetero-Diels–Alder reaction of butadiene with formaldehyde and thioformaldehyde were studied by a CASSCF molecular orbital method. The energy barrier of the concerted reaction of butadiene with formaldehyde is about 21 kcal/mol higher than that of butadiene with thioformaldehyde at the CAS-MP2 calculation level. For the stepwise reaction paths, the energy barrier for the first step process of the reaction of butadiene with formaldehyde is about 17 kcal/mol above that of butadiene with thioformaldehyde. The concerted pathways for both systems are more favorable by 9–12 kcal/mol than the stepwise pathways. The electronic mechanisms for the concerted reactions of both reaction systems are also discussed by a CiLC analysis.     

Catalytic effect of copper on the hexacyanoferrate(III)-cyanide redox reaction-I The uncatalysed and catalysed reactions

A kinetic study of the hexacyanoferrate(III)-cyanide redox reaction has been made in connection with development of a new catalytic method for copper. The reaction kinetics change with time from first- to second-order dependence with respect to hexacyanoferrate(III). The reaction is nearly inverse first-order with respect to hexacyanoferrate(II) and first-order with respect to cyanide. The reaction shows a strong positive primary salt effect, but a very small increase in the reaction rate with temperature is found. A parallel reaction proceeds with a first-order dependence with respect to hydroxide. A tentative mechanism is proposed for the first reaction, involving the formation of cyanogen radicals. The second reaction corresponds to the well-known decomposition of hexacyanoferrate(III) in alkaline medium. The catalysed reaction exhibits similar kinetics with respect to hexacyanoferrate(II) and (III) but is zero-order with respect to cyanide and hydroxide and first-order with respect to catalyst. The proposed mechanism involves two consecutive interactions of the hexacyanoferrate(III) with copper(I) and with copper(II) cyanide complexes respectively, followed by a 2-electron oxidation of a co-ordinatively bridging cyanide group.     

Mathematical modeling of cyclic voltammetry for EC<Subscript>2</Subscript> reaction

The non-steady-state concentration for an EC reaction at planar electrode is derived. The analytical expression for the concentration for EC reaction is reported for small and large value of reaction rate. The asymptotic expression for the non-steady-state current for EC reaction is also derived. The analytical solutions for normalized current response were formulated using the method of Laplace transformation. The concentration and current are compared with available limiting case results, and are found to be in good agreement.     

The use of polymer-bound triphenylphosphine in the stereochemical inversion of secondary alcohols

Polymer-bound triphenylphosphine can replace triphenylphosphine in the Mitsunobu reaction to generate stereochemically inverted secondary alcohols. This method is comparable with the standard Mitsunobu reaction in terms of inversion of stereochemistry, yield, and reaction time, even for sterically very hindered secondary alcohols. The special merit of this reaction is that the excess polymer-bound triphenylphosphine and its by-products are easily removed by filtration from the reaction products.