Primary Transformation Rate Measurements Through Differential Scanning Calorimetry

Summary. The primary crystallization of molten alloy systems at high undercooling is studied by a precise quantitative analysis of the calorimetric signal obtained during the transformation in terms of the reaction rate under isothermal and continuous heating regimes. It is shown that, under specific conditions, namely, stoechiometric primary precipitates, generalized relationships for the crystallization enthalpy and the reaction rate may be obtained.     

GC-MS测定二氯甲烷溶液中的氯化苦及测定过程中产生的新生化合物

以GC—MS联用测定了二氯甲烷溶液中的氯化苦,并通过改变进样口温度和传输线温度研究温度变化对测定氯化苦的影响。当进样口温度高于200℃时,氯化苦会与二氯甲烷发生明显反应,形成新的产物。通过比较分别以氘代二氯甲烷和二氯甲烷做溶剂时所生成产物的GC—MS质谱图的不同,推测了反应产物的结构。并比较了正离子化学电离方式和负离子化学电离方式测定氯化苦的灵敏度。     

曝光强度对卤化银微晶中载流子行为及其陷阱效应的影响

针对卤化银感光材料潜影形成过程中光作用动力学问题,分析了曝光强度对光生载流子行为和电子陷阱效应的影响,认为伴随着曝光强度的增加,影响光电子衰减的因素由电子陷阱起主要作用演化到电子陷阱和复合中心共同起作用进而演化到复合中心起主要作用.     

The effect of phenolates in the (salen)Mn-catalyzed epoxidation reactions

By addition of 2,4,6-tri-tert-butylphenolate in the Mn(salen) catalyzed epoxidation of cis-alkenes with iodosobenzene, essentially pure trans-epoxides can be obtained.     

Reaction of aryl azides with tris(trimethylsilyl)silyllithium: Synthesis of tmeda or thf adducts of [Li{N(Ar)Si(SiMe3)3}] and 1,4-trimethylsilyl migration from oxygen to nitrogen

Reaction of ArN₃ (Ar = Ph, p-MeC₆H₄, 1-naphthyl) with [Li{Si(SiMe₃)₃}(thf)₃] yielded lithium amides [Li{N(Ar)Si(SiMe₃)₃}L] (L = tmeda or (thf)₂). Similar treatment of o-phenylene diazide with 2 equiv. of [Li{Si(SiMe₃)₃}(thf)₃] formed dilithium diamide complex 4. Reaction between o-Me₃SiOC₆H₄N₃ and [Li{Si(SiMe₃)₃}(thf)₃] afforded, via 1,4-trimethylsilyl migration from oxygen to nitrogen, [Li{OC₆H₄{N(SiMe₃)Si(SiMe₃)₃}-2}]₂ (5). The structures of complexes 3 and 5 have been determined by single crystal X-ray diffraction techniques.     

氟分子与乙烯反应的直接动力学模拟

Direct dynamics within the framework of DFT was used to study the long-time puzzling mechanism of the reaction between F2 and ethylene. Three types of reactions are widely accepted : F atom elimination reaction, HF elimination reaction and the addition reaction. Several reaction mechanisms have been proposed, but only the radical mechanism can reasonably explain the initial reaction at low temperature. In this article, our calculations support the radical mechanism and the reaction mechanisms of the three reactions, and they are described in detail by trajectory simulation. The reactions in a cryogenic matrix with the reaction mechanism were also discussed.     

自然和人工光合作用水裂解催化剂

近年生物光合作用水裂解催化中心的结构研究取得重要进展,为人工模拟光合作用水裂解研究提供了理想的蓝图。人工模拟生物水裂解催化中心、制备高效和廉价的人工水裂解催化剂、获得电能和(或)氢能被认为是解决人类所面临的能源危机和环境污染问题的理想途径。这方面的研究具有重要科学意义和应用价值,同时也是广受关注的重大科学前沿。本文对最近生物水裂解催化中心和其人工模拟研究进展进行了评述。     

Theoretical Study on Mechanism and Kinetics of Reaction of O(3P) with Propane

The reaction of C₃H₈+O(³P)→C₃H₇+OH is investigated using ab initio calculation and dynamical methods. Electronic structure calculations for all stationary points are obtained using a dual-level strategy. The geometry optimization is performed using the unrestricted second-order Møller-Plesset perturbation method and the single-point energy is computed using the coupled-cluster singles and doubles augmented by a perturbative treatment of triple excitations method. Results indicate that the main reaction channel is C₃H₈+O(³P)→i-C₃H₇+OH. Based upon the ab initio data, thermal rate constants are calculated using the variational transition state theory method with the temperature ranging from 298 K to 1000 K. These calculated rate constants are in better agreement with experiments than those reported in previous theoretical studies, and the branching ratios of the reaction are also calculated in the present work. Furthermore, the isotope effects of the title reaction are calculated and discussed. The present work reveals the reaction mechanism of hydrogen-abstraction from propane involving reaction channel competitions is helpful for the under-standing of propane combustion.     

RP-3高温氧化初始阶段反应机理的ReaxFF MD模拟

本文采用ReaxFF MD方法对一种较新的RP-3四组分替代燃料模型的高温氧化过程进行了研究。利用作者所在课题组研发的独特分析工具VARxMD,对燃烧过程中主要物种(燃料分子、O₂、C₂H₄、·CH₃)随时间和温度的演变规律及其化学反应进行了系统分析。ReaxFF MD模拟得到的燃料和氧气消耗量、乙烯和甲基自由基的生成量与相同温度和初始压力条件下CHEMKIN的计算结果处于同一量级,同时获得了详细的物质结构信息和反应列表。进一步对模拟得到的反应机理形式进行观察后发现,模拟获得的机理形式与文献中的描述一致。对燃料分子第一步反应数量的统计发现,其类型主要为攫氢反应和分子内断裂反应,且后者占主导;燃料分子第一步反应数量的统计也定性展现了不同燃烧条件下各类反应发生的可能性。对氧元素相关的反应分析发现,氧分子和C₁-C₃小分子发生的反应所占比例较大,能在一定程度上为机理简化提供有益线索。在对反应机理分析的基础上获得了RP-3四组分替代燃料体系高温氧化过程的化学反应网络。我们认为,ReaxFF MD反应分子动力学模拟、结合VARxMD对模拟结果深入分析的方法是有潜力系统认识燃料氧化反应机理的新方法,对构建燃料的燃烧反应机理库有一定的帮助。     

含有手性连接基的双噁唑啉配体及其在不对称催化反应中的应用

综述了具有手性连接基的双噁唑啉配体及其主要类型, 并介绍了它们参与的不对称催化反应.