反应N+NH→N2+H的态-态量子动力学研究

采用在MRCI/aug-cc-pVQZ水平上构建的N₂H基态势能面, 并运用Chebyshev实波包法研究了N + NH→N₂ + H反应的量子动力学, 如反应几率、 积分截面以及产物振转态分布等. 在50~500 K温度范围内, 该反应的速率常数随着温度升高而递增, 与基于其它势能面的理论结果吻合. 然而, 在室温条件下, 所有理论计算的速率常数均显著大于实验值.     

F+H2→HF+H反应的全量子态分辨的散射动力学研究

A crossed molecular beams, state-to-state scattering study was carried out on the F+H2→HF+H reaction at the collision energy of 5.02 kJ/mol, using the highly sensitive H atom Rydberg tagging time-of-flight method. All the peaks in the TOF spectra can be clearly assigned to the ro-vibrational structures of the HF product. The forward scattering of the HF product at v′=3 has been observed. The small forward scattering of the HF product at v′=2 has also been detected. Detailed theoretical analysis is required in order to fully understand the dynamical origin of these forward scattering products at this high collision energy.     

维生素C氧化反应的研究: H2O2-Cu^2^+-磷酸体系中的反应动力学

研究了在铜离子存在时的弱酸性条件下, 用过氧化氢氧化维生素C, 并用直接分光光度法测定未变化的酸, 表明维生素C的催化氧化是以链式反应机制进行的.     

气相中CrO2+和H2反应的理论研究

用密度泛函UB3LYP/6-311++G(3df, 3pdpd)//6-311G(2dd, p)方法计算研究了在二重态和四重态两个势能面上的气相反应：CrO₂⁺ + H₂→CrO⁺+ H₂O. 对影响反应机理和反应速率的势能面交叉进行了讨论, 并运用Hammond 假设和Yoshizawa 等的内禀反应坐标(IRC)单点垂直激发计算的方法找出了势能面交叉点(crossing point (CP)). 运用碎片分子轨道(fragment molecular orbital(FMO))理论, 对初始复合物2IM1和4IM1的轨道相关进行了分析, 解释了CrO₂⁺活化H—H σ键及H₂迁移的机理.     

反应Si+HCl→SiCl+H的直接动力学研究

利用从头算直接动力学方法，研究反应Si HCl→SiCl H的动力学性能，在QCISD／6－311＋G（d,p)和CCSD（T）／aug-cc-pvtz(单点）水平上，得到体系的势能面信息，进而利用变分过渡态理论计算了反应的速率常数及其与温度的关系。计算结果与实验符合得很好。     

Waddington反应机理中β-断键反应类动力学研究

β-羟基烷基过氧自由基(β-HOROO·)是烯烃低温燃烧的主要中间体,其主要消耗通道为Waddington反应通道,即首先分子内发生1,5-H迁移生成β-氢过氧烷氧自由基(β-HOORO·),随后β-HOORO·发生β-断键生成醛(或酮)和OH自由基。本文针对该反应通道的第二步反应,对不同烷基R的β-HOORO·的β-断键反应类的动力学开展了系统研究。对该反应类,根据β-HOORO中连接-OOH的C原子(C_(-OOH))和连接-O·的C原子(C_(-O·))类型不同,划分为不同子类,并对每一子类选取不同取代基大小作为代表反应,开展了能垒和速率常数的规律研究。物种几何结构优化和反应能垒的计算均在M06-2X/6-311++G(d,p)水平进行,反应的高压极限速率常数则采用过渡态理论计算。本文构建了该类反应的速率规则和Evan-Polanyi线性自由能关系,考察了C_(-OOH)和C_(-O·)不同类型以及取代基大小对反应动力学参数的影响。本文的研究为烯烃低温燃烧中重要的β-HOORO·发生β-断键反应类提供了准确的动力学参数,有助于烯烃燃烧详细机理的构建以及机理自动生成。     

Cl+C2H6→HCl+C2H5反应的准经典轨线研究

用三原子模型的准经典轨线方法研究了Ｃｌ与Ｃ２Ｈ６（ｖ＝０，ｊ）的反应。计算结果表明，反应产物ＨＣｌ的角度分布基本上为各向同性，其振动分布处于基态，与实验结果相一致。对反应轨线的研究表明，该反应为一直接反应，而且反应碰撞在低及高的碰撞参数下的机理不一样，在低碰撞参数下反应碰撞是直接完成的，产物ＨＣｌ以向后散射为主，转动基本上是冷的，但比高碰撞参数下的热。在高的碰撞参数下则生成短寿命的碰撞复合物，产物     

CH_3CN+CH_3→CH_2CN+CH_4氢消除反应的直接动力学研究

采用直接动力学方法,对乙腈与甲基的反应进行了理论研究.在BHandHLYP/6-311G(d,p)和MP2/6-311G(d,p)水平下获得,稳定点的几何结构、振动频率及最小能量路径(MEP),在G3(MP2)和MC-QCISD水平下对能量信息进一步确认.利用正则变分过渡态理论,结合小曲率隧道效应校正(CVT/SCT)方法计算了该反应在220K～2000K的速率常数,与实验值符合得很好.     

N2H2脱氢反应和异构化反应的IRC解析

用内禀反应坐标(IRC)法讨论了N₂H₂的脱氢反应机理和异构化反应机理,较完整地阐述了N₂H₂在位能面上的重排和离解过程.     

Reaction of H2 and N+ Ion under Titan's Atmosphere

The thermochemical properties of reaction N⁺+H₂→NH⁺+H have been computed under Titan's atmosphere conditions. It is observed that this reaction is an endothermic reaction and cannot proceed forward spontaneously under low temperature. The rate for this reaction at 300 K has been calculated as k=4.16×10^?10 cm³·mol^?1·s^?1. The reaction barrier is 109.847 kJ·mol^?1 at 298.15 K, which is probably too high to allow this reaction to occur in the atmosphere of Titan. The kinetic properties of the reaction are calculated at a pressure of 90 Pa and a temperature ranging from 1 to 5000 K. It is found that this reaction has a very low reaction rate under low temperature in Titan's atmosphere and that the rate decreases drastically with decreasing temperature. This result should be applicable to interstellar place with low temperature values. The results are compared with those obtained from experiments.     

Reaction HFCO + 2H2O — Calculated Mechanisms

Three possible reaction mechanisms of methanoyl fluoride with 2H₂O include a concerted and a stepwise hydrolysis of HFCO into HCOOH + HF, and a pure catalytic decomposition of HFCO into HF + CO. Among these, the two H₂O molecules acting as catalyst to decompose HFCO has the lowest calculated barrier, 25.1 kcal/mol with respect to the reactant‐adduct complex, whereas the barriers for the concerted and stepwise hydrolytic reactions in which one H₂O acts as a reactant and the other H₂O as catalyst are similar, 30.8 kcal/mol for concerted and 29.9 kcal/mol for stepwise. The formation of transoid HCOOH in the hydrolysis of HFCO is more favorable than cisoid HCOOH.     

Theoretical Studies on N2H+O Reaction

The N2H＋O potential energy profile was studied at the CCSD（T）/6-311G＋＋（df,p）//MP2/6-311G（d,p） level. Reactions associated with four intermediates（cis-HNNO, trans-HNNO, NNHO, and NNOH） were investigated. The results indicate that N2H＋O reaction toward H＋N2O is more favored than that toward N2＋OH, consistent with previous experimental studies. The pathways for the two reactions are found to go through cis-HNNO, transition state, and finally to the products. The N2H＋O→NH＋NO reaction was studied in detail. Product NO in such a reaction is likely to occur via cis-HNNO, followed by trans-HNNO, and finally dissociates into NH＋NO. These results suggest that N2H＋O→NH＋NO is an important channel in NO production.     

二级反应速率常数与活化能计算问题的讨论

针对物理化学参考书中个别有关化学反应速率常数的计算问题进行讨论。计算二级反应的速率常数k时,套用半衰期公式要注意与反应计量方程式的表达形式相对应;对于理想气体反应使用Arrhenius公式计算活化能时,要注意反应速率常数k_c和k_p以及相应活化能E_ac和E_ap的区别。以帮助学生在计算过程中有正确的理解和认识。     

BH+2与C2H2反应势能面的量子化学研究

用B3LYP/6-311G(d,p) 密度泛函方法和高级电子相关的CCSD(T)/6-311G(2df,p)偶合簇法研究BH+2与C2H2反应势能面. 结果表明 该势能面上存在(a) H2B+*C2H2, (b) HBCHCH2+, (c) H2BCCH+2和(d) H2*BHCCH+四种异构体, 其中(b)能量最低且在动力学上最稳定, (a), (c)和(d)在动力学上均不稳定; BH+2通过对C2H2的分步亲电加成以及随后的氢迁移和H2消除等反应形成离解产物HBCCH++H2, 该反应不需要活化能且大量放热. 计算结果有助于深入了解BH+2等缺电子硼氢正离子的反应行为.     

CH2 CHF与臭氧反应机理的量子化学研究

用量子化学MP2方法,在6-311+ +G(d,p)基组水平上研究了烯烃CH2CHF与臭氧反应的机理,对氟代乙烯臭氧化反应Criegee机理进行了系统的计算,全参数优化了反应过程中反应物、中间体、过渡态和产物的几何构型,在QCISD(T)/6-311+ +G(d,p)水平上计算了它们的能量.并对它们进行了频率分析,以确定中间体和过渡态的真实性.研究结果表明,氟代乙烯与臭氧反应沿Criegee机理是可信的、合理的.同时研究还发现,就氟代乙烯与臭氧反应活性而言,其控制步骤的位垒较低,可以说氟代乙烯与臭氧反应活性较强,也就是说氟代乙烯对臭氧的损耗较大.     

Reaction Mechanism and Product Branching Ratios of OH+C2H3F Reaction: A Theoretical Study

Ab initio CCSD(T)/CBS//B3LYP/6-311G(d, p) calculations of the potential energy surface for possible dissociation channels of HOC\begin{document}$_2$\end{document}H\begin{document}$_3$\end{document}F, as well as Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of rate constants, were carried out, in order to predict statistical product branching ratios in dissociation of HOC\begin{document}$_2$\end{document}H\begin{document}$_3$\end{document}F at various internal energies. The most favorable reaction pathway leading to the major CH\begin{document}$_2$\end{document}CHO+HF products is as the following: OH+C\begin{document}$_2$\end{document}H\begin{document}$_3$\end{document}F\begin{document}$\rightarrow$\end{document}i2\begin{document}$\rightarrow$\end{document}TS14\begin{document}$\rightarrow$\end{document}i6\begin{document}$\rightarrow$\end{document}TS9\begin{document}$\rightarrow$\end{document}i3\begin{document}$\rightarrow$\end{document}TS3\begin{document}$\rightarrow$\end{document}CH\begin{document}$_2$\end{document}CHO+HF, where the rate-determining step is HF elimination from the CO bridging position via TS11, lying above the reactants by 3.8 kcal/mol. The CH\begin{document}$_2$\end{document}O+CH\begin{document}$_2$\end{document}F products can be formed by F atom migration from C\begin{document}$_\beta$\end{document} to C\begin{document}$_\alpha$\end{document} position via TS14, then H migration from O to C\begin{document}$_\alpha$\end{document} position via TS16, and C-C breaking to form the products via TS5, which is 1.8 kcal/mol lower in energy than the reactants, and 4.0 kcal/mol lower than TS11.     

SnO2/CeO2表面反应速率方程和分子反应几率

The principle and experimental law of testing sets to test reaction temperature change were introduced. Using “powder sputtering plane thin-film SnO2/CeO2 alcohol sensor”, the reaction temperature change was tested and the law of versus gas concentration was given by the inserting method. The rate equation of surface reaction was deduced and reaction probability of surface molecule was calculated. The general reaction rate equation includes two kinds of experiential formula—hyperbolic and power function formula and the concept of molecule reaction probability is minor, which in general is 10-3-10-5.