反应类等键反应方法及类反应热动力学参数计算

本文提出了反应类等键反应方法,将通常用于热力学性质计算的等键反应方法推广用于类反应中反应势垒和反应焓变的计算. 对碳氢燃料低温燃烧反应机理中的一类重要反应类：?烷基自由基过氧化氢裂解生成烯烃和HO2自由基的反应势垒和反应焓变进行了计算. 通过对该类16个反应中的5个代表反应分别在不同计算水平HF、DFT、MP2、CCSD(T)的比较计算发现,采用等键反应方法可在较低从头算级别计算得到类反应较高精度的反应势垒,提高了计算的效率和精度. 本文采用反应类等键反应方法在B3LYP/6-311G(d,p)计算水平对该类16个反应进行了反应势垒和反应焓变的计算,并建立了反应势垒和反应能的线性自由能关系：delta V=71.02+0.41?delta E.     

Implicit versus explicit solvent in free energy calculations of enzyme catalysis: Methyl transfer catalyzed by catechol O-methyltransferase

We compare free energy calculations for the methyl transfer reaction catalyzed by catechol O-methyltransferase using the quantum mechanical/molecular mechanical free energy method with implicit and explicit solvents. An analogous methylation reaction in a solution is also studied. For the explicit solvent model, we use the three-point transferable intermolecular potential model, and for the implicit model, we use the generalized Born molecular volume model as implemented in CHARMM. We find that activation and reaction free energies calculated with the two models are very similar, despite some structural differences that exist. A significant change in the polarization of the environment occurs as the reaction proceeds. This is more pronounced for the reaction in a solution than for the enzymatic reaction. For the enzymatic reaction, most of the changes take place in the protein rather than in the solvent, and, hence, the benefit of having an instantaneous relaxation of the solvent degrees of freedom is less pronounced for the enzymatic reaction than for the reaction in a solution. This is a likely reason why energies of the enzyme reaction are less sensitive to the choice of atomic radii than are energies of the reaction in a solution.     

低热固相反应的反应机理研究(Ⅰ)——冷融熔机理和冷溶熔机理的模型

本文提出了低热固相反应的冷融熔机理和冷溶熔机理,其中冷融熔机理主要针对于不含结晶水的反应体系,冷溶熔机理主要针对于含结晶水的反应体系,并对低热固相反应动力学提出冷融熔/冷溶熔、扩散、反应、成核、生长的五步机理。两种机理都避开了分子在固相晶格中的扩散,从而对低热固相反应的扩散问题进行了有效的解释,并给出了低热固相反应的热力学和动力学判据。     

Phase and chemical equilibria in the transesterification reaction of vegetable oils with supercritical lower alcohols

Calculations of thermodynamic data are performed for fatty acid triglycerides, free fatty acids, and fatty acid methyl esters, participants of the transesterification reaction of vegetable oils that occurs in methanol. Using the obtained thermodynamic parameters, the phase diagrams for the reaction mixture are constructed, and the chemical equilibria of the esterification reaction of free fatty acids and the transesterification reaction of fatty acid triglycerides attained upon treatment with supercritical methanol are determined. Relying on our analysis of the obtained equilibria for the esterification reaction of fatty acids and the transesterification reaction of triglycerides attained upon treatment with lower alcohols, we select the optimum conditions for performing the reaction in practice.     

Reaction path synthesis methodology for waste minimization

Being the core of whole process, a chemical process is a key step for reducing waste generation. Therefore, to organize a reasonable reaction path is very important for reducing waste emission. Because of the large amount of the feasible reaction path and other factors in a chemical reaction system, the opti-mizing for reaction path is difficult. Since the reaction path synthesis problem has presented, lots of re-searchers focused on it. At the beginning, only chem-ists took the research work,…     

Theoretical studies of reaction mechanism in chemistry

After defining reaction mechanism, reaction path, reaction coordinate, reaction profile, and classical trajectories, dynamic and static approaches suitable (or promising) for analysis of reaction mechanism are critically discussed.     

Theoretical study on the alkaline hydrolysis of methyl thioacetate in aqueous solution

A base-catalyzed hydrolysis reaction of thiolester has been studied in both gas and solution phases using two ab initio quantum mechanics calculations such as Gaussian09 and CPMD. The free-energy surface along the reaction path is also constructed using a configuration sampling technique, namely, the metadynamics method. While there are two different reaction paths obtained for the potential profile of the base-catalyzed hydrolysis reaction for thiolester in the gas phase, a triple-well reaction path is computed for the reaction in the solution phase by two quantum mechanics calculations. Unlike the S(N)2 mechanism (a concerted mechanism) found for the gas-phase reaction, a nucleophilic attack from the hydroxide ion on the carbonyl carbon to yield a tetrahedral intermediate (a stepwise mechanism) is observed for the solution-phase reaction. Moreover, the energy profiles computed by these two theoretical calculations are found to be very comparable with those determined experimentally.     

脯氨酸催化的不对称有机反应

脯氨酸作为一种结构简单、商品化的、廉价小分子手性催化剂,在多种不对称催化反应中表现出非常好的催化性能,本文综述了近年来脯氨酸直接催化的不对称有机反应涉及Aldol反应,Mannich反应,Michael反应,Diels-Alder反应,直接α-胺化反应,α-氧胺化反应,Baylis-Hillman反应,还原反应和氧化反应的进展并展望了其应用前景。     

液态聚乙二醇作为绿色反应介质在有机反应中的应用

低分子量的液态聚乙二醇（PEG）作为一种新型的绿色有机反应溶剂正受到人们的极大关注。PEG具有好的热稳定性、不挥发、不易燃、无毒、生物可降解、廉价易得,以及易于回收和循环使用。此外,PEG可以溶解众多的有机化合物和有机金属配合物。因此,PEG作为有机溶剂的替代品和作为均相催化剂的载体已经成功地应用到许多有机反应中,它们包括还原反应、氢化反应、氧化反应、不对称双羟基化反应、Heck反应、Suzuki交叉偶联反应、Michael加成反应、不对称Aldol反应、Baylis-Hillman反应、脂肪酶催化的反应和聚合反应等。本文对这一领域的研究进展作一综述。     

甘氨酸螯合钙的合成与性能研究

以甘氨酸和金属钙盐为原料,采用水体系合成法制备甘氨酸钙螯合物,探讨不同反应温度、反应时问、反应体系pH等对产品产率的影响,从而确定反应的最佳条件,并对甘氨酸钙螯合物采用傅里叶红外光谱FT-IR进行表征。实验结果表明,合成甘氨酸钙螯合物的最适反应条件是,反应体系pH为5～6,反应时间为2～3h,反应温度为70～80℃。     

硫碘循环制氢中Bunsen反应新方法的研究进展

热化学硫碘(S-I)循环分解水是目前有较高效率且可以在相对较低温度条件下进行的制氢方法之一。 其中的Bunsen反应作为循环的核心步骤尤为重要。 为了更方便有效地分离Bunsen反应的生成物硫酸与氢碘酸,许多学者研究了Bunsen反应的新方法。 本文对非水溶剂中的Bunsen反应和电化学Bunsen反应两种新方法进行了综述。 讨论了非水溶剂中实现反应生成物分离的方法,对比了各种非水溶剂的性质及其优缺点。 目前,所发现的溶剂在分离生成物方面已达到要求,可用于Bunsen反应,但溶剂的回收再利用比较困难。 概述了电化学Bunsen反应的研究现状,对目前在电化学Bunsen反应中有突破进展的两个团队的工作进行了对比。 现今对该方法的探讨主要集中在反应基础特性方面,未来可以加强电化学Bunsen反应机理、反应电池结构设计与优化、以及新型S-I循环系统构造的研究。     

Toward De Novo Catalyst Discovery: Fast Identification of New Catalyst Candidates for Alcohol-Mediated Morita–Baylis–Hillman Reactions**

Recently we have demonstrated how a genetic algorithm (GA) starting from random tertiary amines can be used to discover a new and efficient catalyst for the alcohol-mediated Morita–Baylis–Hillman (MBH) reaction. In particular, the discovered catalyst was shown experimentally to be eight times more active than DABCO, commonly used to catalyze the MBH reaction. This represents a breakthrough in using generative models for catalyst optimization. However, the GA procedure, and hence discovery, relied on two important pieces of information; 1) the knowledge that tertiary amines catalyze the reaction and 2) the mechanism and reaction profile for the catalyzed reaction, in particular the transition state structure of the rate-determining step. Thus, truly de novo catalyst discovery must include these steps. Here we present such a method for discovering catalyst candidates for a specific reaction while simultaneously proposing a mechanism for the catalyzed reaction. We show that tertiary amines and phosphines are potential catalysts for the MBH reaction by screening 11 molecular templates representing common functional groups. The method relies on an automated reaction discovery workflow using meta-dynamics calculations. Combining this method for catalyst candidate discovery with our GA-based catalyst optimization method results in an algorithm for truly de novo catalyst discovery.     

三芳胺合成的研究进展

三芳胺化合物的合成方法主要有3种:(1)非金属催化的胺化反应;(2)铜催化的Ullnann反应,包括使用过量铜粉为催化剂的传统的Ullmann反应、使用相转移催化剂的Ullmann反应以及使用配体的post-Ullmann反应;(3)钯催化的Buchwald-Hartwig反应.该类反应活性的关键是配体的选择,根据配体结构的不同可分为双膦螯合型配体、单膦配体和非膦配体.对该类化合物的这几种合成方法的研究进展进行了总结.     

Domino carbopalladation-cross-coupling for the synthesis of 3,3-disubstituted oxindoles

This study examines a domino carbopalladation-cross-coupling reaction for the formation of valuable oxindole scaffolds. Furthermore, the reaction sequence forges vicinal stereocenters in a stereospecific manner through the formation of two carbon-carbon bonds and, thereby, rapidly generates complexity. The reaction gives high yields for a variety of acrylamide substrates, and various organoboranes have also been evaluated for the cross-coupling. This work offers insight into the relative rates determining a successful carbopalladation-cross-coupling reaction and how to favor the desired reaction pathway.     

Correlation of relative rates of PdCl(2) oxidation of functionalized acyclic alkenes versus alkene ionization potentials, HOMOs, and LUMOs.

Investigations of the title reaction, carried out by plotting logs of the relative reaction rates vs IPs, vs HOMOs, and vs LUMOs, reveal multiple nearly parallel lines of correlation with small negative slopes in each. Overall, the natural grouping into monosubstituted and disubstituted alkenes gives better correlations than that obtained by using all alkenes. Comparison with analogous plots for other reactions indicates that the mechanism for this reaction has similarities to that for hydroboration, the major difference being that the lines in the plots for hydroboration have positive slopes, indicating an electrophilic rate-determining step involving the pi electrons, while those for the title reaction have small negative slopes, indicating a nucleophilic rate-determining step. Of the two reaction mechanisms proposed for the title reaction, only one has a nucleophilic attack at the complexed alkene as the rate-determining step, and therefore, this work supports that reaction mechanism.     

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.     

壳聚糖席夫碱钯催化碘代苯与丙烯酸乙酯反应

以水杨醛与壳聚糖反应制得的壳聚糖席夫碱配体再与PdCl2反应制得了壳聚糖席夫碱钯催化剂。研究了该催化剂对碘代苯(PhI)与丙烯酸乙酯(EA)偶联生成反式肉桂酸乙酯反应的催化性能。考察了原料比、缚酸剂种类及其用量、反应温度、溶剂、催化剂用量、反应时间等因素对该反应的影响,确定了该催化反应的最佳反应条件。该催化剂经过滤分离、溶剂洗涤,循环使用4次仍有较高的催化活性。     

苯并噻唑-2-甲醛合成方法的改进

以邻氨基苯硫酚为原料,先与羟基乙酸反应合成2-羟甲基苯并噻唑,然后通过氧化反应生成苯并噻唑-2-甲醛。对比了几种氧化剂的效果,发现二氧化锰氧化的效果最好。优化的反应条件为,2-羟甲基苯并噻唑与二氧化锰的摩尔比为1∶8,回流反应8h,产率可达90.2%。该方法适合苯并噻唑-2-甲醛及其衍生物的大规模生产。     

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.     

水相钯催化Suzuki反应

钯催化的Suzuki反应是构建Csp2—Csp2键的主要方法之一,已广泛应用于医药、天然产物及先进功能材料等联芳类化合物的合成.近年来,水相Suzuki反应引起了人们的高度关注.对以纯水及水/有机混溶剂为介质的水相Suzuki反应的研究进展作一综述,特别是围绕如何解决水相Suzuki反应活性的问题,以催化体系为主线,重点介绍了水溶性配体/钯、表面活性剂、微波促进的非水溶性配体/钯及无配体钯等催化体系在水相Suzuki反应中的应用.