Direct partial oxidation of methane to methanol： Reaction zones and role of catalyst location

Direct partial oxidation of methane to methanol was investigated in a specially designed reactor. Methanol yield of about 7%-8% was obtained in gas phase partial oxidation. It was proposed that the reactor could be divided into three reaction zones, namely pre-reaction zone, fierce reaction zone, and post-reaction zone, when the temperature was high enough to initiate a reaction. The oxidation of methane proceeded and was completed mostly in the fierce reaction zone. When the reactant mixture entered the post-reaction zone, only a small amount of produced methanol would bring about secondary reactions, because molecular oxygen had been exhausted in the fierce reaction zone. A catalyst, if necessary, should be placed either in the pre-reaction zone, to initiate a partial oxidation reaction at a lower temperature, or in the fierce reaction zone to control the homogeneous free radical reaction.     

低温常压氧气液相氧化邻硝基甲苯的表观动力学研究

文章讨论了低温常压条件下氧气液相氧化邻硝基甲苯的表观动力学。在确定了邻硝基苯甲醛和邻硝基苯甲酸为主要产物的基础上，建立了连串反应模型，根据不同温度下的实验数据，确立了首步一级，第二步二分之一级的反应级数，进而求得了两步反应的速率参数k1、k2，并将实验数据与理论计算值相比较，表明在较低温度(0℃以下)下，拟合的级数与使用符合较好。     

Synthesis of imidazo-1,4-oxazinone derivatives and investigation of reaction mechanism

In this study, nine different C-2 aroyl imidazole derivatives were synthesized in a one pot reaction with two steps, and the reduction reactions of these derivatives with NaBH₄ were carried out under mild conditions. Substitution reaction of obtained imidazo methanol derivatives with chloroacetylchloride reagent and ring reaction of substitution products were investigated. It was determined that 1,4-imidazoxazinone derivative was obtained as a result of the cyclization reaction. The intermediate products obtained during the cyclization reaction were isolated, and the path of the reaction under different conditions was discussed.     

Kinetics of gas-phase hydrolysis of ethyl acetate catalyzed by immobilized lipase

Reactions catalyzed by supported enzymes present important advantages when compared with those in aqueous media or organic solvents: separation of enzymes from substrate is easily accomplished, enzyme stability may be improved, and control of the reaction products is more accurate. We present the experimental results of the kinetic study of ethyl acetate hydrolysis in gaseous phase catalyzed by a commercial immobilized lipase (Lipozyme IM; Novo Nordisk). The hydrolysis reaction was studied as a function of ethyl ester and water partial pressure at a constant temperature of 318 K. The amount of biocatalyst used was varied between 100 and 300 mg, and the reaction was studied in a flow-through glass microreactor. Under the conditions used, water was an important parameter in the gas-phase reaction. Activation energy was 24.8 kJ/mol and the overall order of reaction was one. Finally a Bi-Bi reaction mechanism is proposed.     

Synthesis of functionalized m-bistrifluoromethylbenzenes via cyclocondensation of 1,1,1,5,5,5-hexafluoroacetylacetone with enamines

The reaction of 1,1,1,5,5,5-hexafluoroacetylacetone with push-pull enamines having a methyl group at the α-position was investigated. It was found that the reaction is sensitive both to the structure of enamines and to reaction conditions. As a result, a set of bistrifluoromethyldialkylanilines and ethyl bistrifluoromethylsalicylate was prepared. Plausible mechanisms and factors influencing the course of the reaction are discussed.     

氯取代丙烷伯氢反应的准经典轨线研究

用准经典轨线方法研究了氯取代丙烷伯氢的反应.采用三体LEPS势能函数构筑势能面.结果表明, 氯取代丙烷伯氢的反应呈现出与氯取代丙烷仲氢反应不同的微观反应进程.对于氯取代丙烷仲氢的反应,只有一种反应通道,反应过程中有碰撞复合物产生.对于氯取代丙烷伯氢的反应,有两种反应通道,一种有碰撞复合物生成,另一种则没有.     

维生素K3电化学反应机理的紫外光谱电化学研究

用薄层池循环伏安法和现场薄层池紫外光谱电化学法研究了维生素Ｋ３（ＶＫ３）在铂电极上的电化学反应机理。薄层池循环伏安实验结果表明：ＶＫ３的电化学反应为二步１ｅ准可逆过程，现场薄层池紫外光谱电化学的实验结果和Ｎｅｒｎｓｔ图解分析表明：电解还原反应的最后产物为２－甲基－１，４－萘酚。该反应偶合有前行化学反应；还原产物经电解氧化的产物为２－甲基－１，４－萘酚。该反应偶合有前行化学反应；还原产物经电解氧化的     

Total synthesis of leustroducsin B

Leustroducsin B was synthesized via a convergent route based on division of the leustroducsin molecule into three segments A, B, and C. Two coupling reactions (Julia coupling reaction and Nozaki-Hiyama-Kishi (NHK) reaction) were employed for coupling of segments A and B: segment A1 for the Julia coupling reaction was prepared by a combination of Sharpless asymmetric epoxidation and an epoxide-cleavage reaction with an organoaluminum reagent, while segment A2 for the NHK reaction was synthesized from optically active alcohol that had previously been prepared by lipase-catalyzed kinetic resolution. Segment B, whose structure was modified with some functional groups, was synthesized from (R)-malic acid by a combination of Wittig reaction and Sharpless asymmetric dihydroxylation, and segment C, containing a cyclohexane moiety, was prepared by asymmetric Diels-Alder reaction. Segment B was first coupled with segment A1 via the Julia coupling reaction, but the yield was low due to unexpected epimerization. The NHK reaction of segment A2 proceeded to give the coupling product in good yield. This product was coupled with segment C via Wittig and Stille coupling reactions, and finally, phosphorylation was carried out by partial hydrolysis of a cyclic phosphate to give leustroducsin B.     

Novel fragmentation reaction of correolide

[reaction: see text] Pentacyclic triterpenoid natural product correolide (1) was converted to ketone 2 via ozonolysis. An unusual fragmentation reaction of ketone 2 with LiCl was discovered. This reaction is general among several similar substrates examined and appears to be specific for the correolide-type E-ring structure (ketone). A mechanism involving a retroaldol reaction, a nucleophilic opening of the epoxide, and a subsequent acetoxy elimination reaction was proposed.     

Effect of phase transfer chemistry, segmented fluid flow, and sonication on the synthesis of cinnamic esters

Wittig reaction under Phase Transfer conditions was performed in a flow reaction system. Different bases, aldehydes, phosphonium salts, and flow reaction parameters were investigated, in absence of a phase transfert catalyst. An improvement of the reaction outcome (yield and reaction time) was achieved through the immersion of the reactor into an ultrasound bath.     

三苯基环戊二烯扩环反应研究

研究在高氯酸银作用下,三苯基环戊二烯扩环氧化生成三苯基取代吡喃盐的反应,并初步探讨了反应机理     

Synthesis of the core structure of cruentaren A

The core structure of the macrolactone cruentaren A (1) was prepared via a ring-closing alkyne metathesis reaction. The corresponding ester 33 was constructed from the benzoic acid derivative 14 and the diol 30. As a key step in the synthesis of acid 14, an aldol reaction resulted in the required anti-OH/Me pattern. The anti-configuration in the stereotetrad of diol 30 was established by a Marshall reaction. [reaction: see text].     

Heat of Reaction of the Hydrolysis-Polymerization Process of Tetraethyl Orthosilicate in Acidic Condition

Heat of reaction of the hydrolysis-polymerization process of tetraethyl orthosilicate with water in acidic condition was investigated to clarify the thermodynamic driving force of sol-gel reactions. Heat of reaction was measured using an isoperibol calorimeter by mixing a dilute tetraethyl orthosilicate (TEOS) ethanolic solution with another solution of water, ethanol, and hydrochloric acid. The temperature change of the reaction cell had been measured more than 24 hours after mixing under the quasi-isothermal condition. Large exothermic reaction (12.9 kJ·mol^–1 for 1 mole of TEOS) due to the hydrolysis of TEOS was observed. A slow exothermic reaction followed it, and after that, the sol-gel reaction was changed to a small endothermic one.     

(±)-耳壳藻内酯的全合成研究(Ⅱ)

以2,6,6-三甲基环己-2-烯-1,4-二酮为原料, 经选择性羰基保护、Wittig反应、脱保护基、 腈基水解和还原等5步反应合成了目标化合物, 总产率可达6.0%.     

The kinetics of the epoxy amine cure reaction from a solvation perspective

This article investigates the role of solvation effects in the autocatalysis reaction of the epoxy–amine cure reaction. A single‐phase three component model was developed encompassing a two‐component reaction mix and a single polymeric product. The reaction was modelled as an S_N2 reaction. Association of the nucleophile with each component in the reaction was defined via a binding constant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3579–3586, 2004     

基本化学反应形式的系统分类

The old classification of basic chemical reactions was evaluated and a new systematic classification of basic reactions was proposed.In the new classification,all the chemical reactions were divided into oxidation-reduction reactions and non-oxidation-reduction reactions,and both can be divided into combination reaction,decomposition reaction and replacement reaction,respectively.In addition,a new class of basic reactions,the complicated decomposition reaction,was appended to reaction system.     

Effect of stoichiometry and diffusion on an epoxy/amine reaction mechanism

The bulk phase kinetics of an epoxy (DGEBA) /amine (DDS) thermoset have been studied using DSC, FTIR, and ¹³C-NMR. In the absence of catalyst, the reaction was found to involve a main exothermic reaction between epoxide and amine hydrogen and a side reaction between tertiary amine formed in the main reaction and epoxide. The main reaction was exothermic while the side reaction had no discernable exotherm. Etherification did not occur to any significant extent. Since only the main reaction is exothermic, DSC was very useful for studying the main reaction kinetics. FTIR was used for determining whether epoxide and amine hydrogen were consumed at different rates as a way of following the side reaction. An IR band previously unused by other investigators was used to monitor the amine hydrogen concentration. NMR confirmed the above mechanism by identifying the formation of a quaternary ammonium ion/alkoxide ion pair as a reaction product of tertiary amine and epoxide. This mechanism has been successfully fit to a rate law valid over the entire extent of reaction. The rate constant for the epoxy/amine addition reaction was found to depend on hydroxide concentration (extent), reaction temperature, and glass transition temperature and included contributions from uncatalyzed and autocatalyzed parts. The side reaction (quaternary ammonium ion formation) formed weak bonds which did not affect the overall system T_g. Both reactions were second order. The rate constants for the main reaction first increase with increasing extent due to autocatalysis by hydroxide before decreasing due to the diffusion limit caused by gelation and vitrification. © 1995 John Wiley & Sons, Inc.     

Study of the reaction between boron trifluoride methanol complex and sodium methoxide

The reaction between boron trifluoride methanol complex and sodium methoxide in methanol solution was investigated using conductivity as the reaction indicator. The reaction conditions were examined and a mechanism of this reaction was proposed. Moreover, proper reaction conditions were proposed for boric acid preparation using this reaction.     

BMD/UP体系非等温固化动力学研究

不饱和聚酯是最常用的一种热固性材料,其力学性能和耐热性是较受关注的两个方面,利用双马来酰亚胺作为第二组分对不饱和聚酯进行耐热改性的工作取得了较好的效果。研究其动力学过程对于固化反应温度、时间等工艺合理优化控制,制备高性能复合材料具有重要意义。考虑到BMD／UP体系中反应的复杂性,本文采用n级动力学模型,进行了非等温动力学研究。     

Kinetics of Reaction of Bromo-epoxy Resin with Oleic Acid catalyzed by Dimethyl benzyl amine

The kinetics of reaction of bromo-epoxy resin with oleic acid in the presence of dimethylbenzylamine catalyst was studied. The reaction is a zero order reaction with respect to oleic acid, first order with respect to epoxy group and 0. 74 order with respect to dimethylbenzylamine. The reaction rate constants at various temperatures and activation energy were determined. The mechanism of this reaction was discussed. Keywords Tetrabromobisphenol-A, Bromo-epoxy resin, Oleic acid kinetics, Reaction mechanism