单取代芳烃的硝化

以甲苯、乙苯、异丙苯、叔丁基苯、氟苯等为硝化底物,通过混酸硝化得到这些单取代芳烃转化率最大时的混酸硝化强度φ。 运用密度泛涵理论,在B3LYP/6-311G**水平上优化了9种单元芳烃的几何构型,计算苯环上C原子电荷分布。 讨论了9种取代基的定位效应,以苯环取代基以外环上C原子总净电荷QRΣC(2~6)表示单取代苯的硝化反应活性与硝化强度φ之间的关系。 实验结果表明,烷基苯、卤苯、硝基苯的硝化反应活性与其混酸硝化转化率达最大时的混酸硝化强度φ呈良好的线性关系。     

杯[4]芳烃四丁醚的选择性硝化

硝化反应;杯[4]芳烃四丁醚的选择性硝化     

芳环硝化反应中碳—碳键的断裂

报道了一例特殊的苯环硝化反应：在硝酸铝作为硝化试剂的条件下,硝化反应是发生在取代烷基与硝基之间而不是苯环上质子与硝基之间。     

杯芳烃与NO2硝化反应的研究

系统地研究了羟基杯[n]芳烃、甲氧基杯[n]芳烃和对特丁基杯[n]芳烃(n＝4, 6, 8)与NO₂气体的硝化反应, 发现可以成功地得到25,26,27,28-四羟基杯[4]芳烃、37,38,39,40,41,42-六羟基杯[6]芳烃以及25,26,27,28-四甲氧基杯[4]芳烃的对位全硝化产物, 产率分别为90%, 70%和40%; 尤其是25,26,27,28-四羟基杯[4]芳烃与NO₂的反应20 min即可完成. 认为共振式酚氧负离子结构是影响该类硝化反应的关键, 并对反应机理进行了探讨.     

硝酸铁对水杨酸甲酯的硝化及位置选择性

用硝酸铁对水杨酸甲酯硝化合成了3-硝基水杨酸甲酯和5-硝基水杨酸甲酯。 考察了反应时间、反应物配比、反应溶液酸碱性对产物收率和位置选择性的影响。 得出较好的反应条件为：反应时间3 h,n(硝酸铁)∶n(水杨酸甲酯)=2∶3。 少量硝酸有利于硝基化反应,且优先生成5-硝基水杨酸甲酯,而碱性不利于硝基化反应,且优先生成3-硝基水杨酸甲酯。 用量化计算解释了硝化反应的位置选择性机理。     

计算分子中原子净电荷的新方法及芳烃亲电取代反应定位效应的定量处理

本文提出一种简捷计算分子中原子净电荷的新方法。用这种方法计算了２３种一元取代苯的原子净电荷。计算所得苯环上碳原子净电荷与其￣（１３）Ｃ－ＮＭＲ化学位移有良好的线性关系。利用苯环上碳原子净电荷及立体参数作为输入参数，应用人工神经网络方法预报２４种一元取代苯硝化反应的邻、间、对位产物产率，结果良好。     

关于酚酞变色机理的量子化学探讨

采用量子化学B3LYP/6-31G＊方法,对酚酞在不同酸度条件下的构型进行了计算,对分子轨道构成和能量进行了分析,从理论上说明了酚酞溶液的变色机理。     

卤代芳烃与芳香化合物的光交联反应——合成与机理

通过研究多种囟代芳烃与芳香化合物的光交联反应,总结出一种高选择性地合成联多芳香化合物的有效方法。同时合成了多种联多芳香化合物并以IR,~1HNMR,MS和元素分析数据确定了它们的结构。其中交联产物3-(1-萘基)香豆素的晶体结构由X射线四圆衍射法解出。进一步研究反应的位置选择性、取代基定位效应、溶剂效应、敏化与猝灭效应等,证明了激发三线态下按电子转移的反应机理。     

NO2气相硝化金刚烷的计算研究

运用密度泛函理论(DFT)和半经验MO-PM3方法研究了NO₂气相硝化金刚烷反应机理. 计算结果表明, NO₂不能直接取代金刚烷H; 在B3LYP/6-311＋＋G(3df,2pd)//B3LYP/6-31G* 较高水平下, 对三个可能机理的反应势垒(E_a)的精确计算表明, 该反应的决速步骤为NO₂中O和N进攻1-H的竞争过程, 且1-硝基金刚烷为主要产物. NO₂中O进攻1-H决速反应过程中, 分子几何、原子自然电荷及IR光谱变化表明, C—H键的断裂和N—H键的形成是一个协同过程; 参与新键形成和旧键断裂原子C(1), H(11), O(28), O(29)和N(27)的原子自然电荷及与其相关的键长、键角有明显的变化. 反应过程中体系偶极矩的变化表明, 极性溶剂能降低反应势垒, 有利于反应的进行.     

丙烯醛光致脱羰机理的量子化学研究

用量子化学方法研究了丙烯醛基态和激发态的反应途径, 通过比较不同反应途径的反应势垒和中间产物构型的稳定性, 从理论上得出该反应的反应机理。     

Reaction Mechanism of Enzyme Studied by Pulse Radiolysis

By virtue of its ability to generate hydrated electrons (e_aq ^?) and various radicals as reductants, the pulse radiolysis technique has been employed for investigating the mechanism of action of peroxidase, cytochrome P-450, and cytochrome oxidase. The oxy forms of hemoproteins, such as myoglobin, peroxidase, and cytochrome P-450, were reduced by hydrated electrons to form the higher oxidation states of these hemoproteins. From these results, the reactive oxygen intermediate of cytochrome chrome P-450 is discussed. The reduction of cytochrome oxidase by the 1-methylnicotinamide radical was investigated. A decrease of the 830-nm band was detected due to the reduction of “visible” copper. After the first phase of the reduction of copper, the return of the 830-nm band corresponding to oxidation of copper was observed. Concomitantly, the absorption at 605 and 445 nm due to the reduction of heme α increased. This suggests that 1-methylnicotinamide radical reacts with the “visible” copper and subsequently flows to heme α by intramolecular migration.     

Mechanism of the Asymmetric Autocatalytic Soai Reaction Studied by Density Functional Theory

The mechanism of the Soai reaction has been thoroughly investigated at the M05‐2X/6‐31G(d) level of theory, by considering ten energetically distinct paths. The study indicates the fully enantioselective catalytic cycle of the homochiral dimers to be the dominant mechanism. Two other catalytic cycles are shown to both be important for correct understanding of the Soai reaction. These are the catalytic cycle of the heterochiral dimer and the non‐enantioselective catalytic cycle of the homochiral dimers. The former has been proved to be not really competitive with the principal cycle, as required for the Soai reaction to manifest chiral amplification, whereas the latter, which is only slightly competitive with the principal one, nicely explains the experimental enantioselectivity observed in the reaction of 2‐methylpyrimidine‐5‐carbaldehyde. The study has also evidenced the inadequacy of the B3LYP functional for mechanistic investigations of the Soai reaction.     

Reaction Mechanism of the Exchange Reaction between CuCl and BaO Studied by Time-Resolved X-ray Absorption Spectroscopy

The solid state reaction 2CuCl+BaO→Cu₂O+BaCl₂ has been examined in situ using energy-dispersive X-ray absorption fine-structure spectroscopy (DXAFS). A high time resolution on the order of seconds between two Cu K-XANES spectra has been achieved by this experimental setup. The spectra suggest that the transformation of CuCl to Cu₂O is preceded by an unidentified, intermediate state. Fingerprint methods as well as principal component analysis have been applied, which confirm the formation of exactly one new intermediate phase. The nature of this phase remains unidentified and could not be elucidated by the experimental investigations.     

谷胱甘肽和Ebselen对胰岛素硝化的抑制及其相互作用机理的研究

生物体内NO和超氧阴离子快速反应生成的过氧亚硝酸根离子(ONOO^-，peroxynitrite)是一种强细胞毒性物质，它诱导蛋白质酪氨酸残基硝化是其损伤生物系统的重要途径之一。为了探讨谷胱甘肽和ebselen对胰岛素硝化的抑制及其相互作用机理，采用UV-Vis、HPLC和ESI-MS等方法，研究了ONOO^-对胰岛素的硝化作用、小分子抗氧化剂谷胱甘肽(GSH)和ebselen对ONOO^-硝化胰岛素的影响以及它们之间的相互作用。结果表明单独的GSH和ebselen对ONOO^--引发的胰岛素硝化均有明显的抑制，而作为谷胱甘肽过氧化物酶(GPx)的底物GSH 与GPx的模型化合物ebselen之间存在相互拮抗作用，经过对其产物分析，确定其机理是GSH和ebselen能够直接反应生成一种加合物，从而抑制了GSH和ebselen各自的抗硝化能力。     

Reaction Kinetics and Mechanism of Selective NO Reduction on a CoZSM-5 Catalyst as Studied by SSITKA

The dynamics of ¹³C transfer from methane to carbon dioxide was studied under the steady-state reaction conditions of selective NO reduction with methane on a CoZSM-5 catalyst at various reactant (NO, CH₄, and O₂) concentrations and temperatures. It was found that the reaction occurs by a two-pathway mechanism with the participation of Co²⁺ sites (or CoO _x clusters) and paired Co²⁺–OH sites localized at the boundary between the clusters and the zeolite; in this case, the rate of the reaction at boundary sites was higher by more than one order of magnitude. Based on the numerical simulation of isotopic response curves, the concentrations of intermediate compounds and the rate constants of particular steps were evaluated; differences in the kinetics via the above reaction pathways were found and analyzed.     

O原子与HNCO反应机理的量子化学及电子密度拓扑研究

采用MP2(Full),B3LYP,QCISD/MP2和CCSD(T)/MP2方法在6-311G(d,p)水平上对O原子与HNCO反应的微观机理进行了理论研究．采用MP2(Full)和B3LYP对反应位能面上的各驻点进行几何构型的全优化,振动分析和IRC计算证实了中间体和过渡态的真实性和相互连接关系．四种方法计算得到了四个反应通道的反应活化能．研究表明,O原子进攻HNCO中的H原子为反应的主要反应通道,该通道中形成了两个分子复合物,电子密度拓扑分析表明这两个分子复合物均为氢键复合物．     

Bonding in Endohedral Metallofullerenes as Studied by Quantum Theory of Atoms in Molecules

Metal–cage and intracluster bonding was studied in detail by quantum theory of atoms in molecules (QTAIM) for the four major classes of endohedral metallofullerenes (EMFs), including monometallofullerenes Ca@C₇₂, La@C₇₂, M@C₈₂ (M=Ca, Sc, Y, La), dimetallofullerenes Sc₂@C₇₆, Y₂@C₈₂, Y₂@C₇₉N, La₂@C₇₈, La₂@C₈₀, metal nitride clusterfullerenes Sc₃N@C_2n (2n=68, 70, 78, 80), Y₃N@C_2n (2n=78, 80, 82, 84, 86, 88), La₃N@C_2n (2n=88, 92, 96), metal carbide clusterfullerenes Sc₂C₂@C₆₈, Sc₂C₂@C₈₂, Sc₂C₂@C₈₄, Ti₂C₂@C₇₈, Y₂C₂@C₈₂, Sc₃C₂@C₈₀, as well as Sc₃CH@C₈₀ and Sc₄O_x@C₈₀ (x=2, 3), that is, 42 EMF molecules and ions in total. Analysis of the delocalization indices and bond critical point (BCP) indicators such as G_bcp/ρ_bcp, H_bcp/ρ_bcp, and |V_bcp|/G_bcp, revealed that all types of bonding in EMFs exhibit a high degree of covalency, and the ionic model is reasonable only for the Ca‐based EMFs. Metal–metal bonds with negative values of the electron‐density Laplacian were found in Y₂@C₈₂, Y₂@C₇₉N, Sc₄O₂@C₈₀, and anionic forms of La₂@C₈₀. A delocalized nature of the metal–cage bonding results in a topological instability of the electron density in EMFs with an unpredictable number of metal–cage bond paths and large elipticity values.     

OBrO+NO反应机理的量子化学研究

用密度泛函B3LYP/6-311+G^**和高级电子相关偶合簇CCSD(T)/6-311+G^**方法研究了OBrO与NO反应的微观机理.优化得到反应路径上的反应物、过渡态、中间体和产物的几何构型,通过频率振动分析对过渡态和中间体进行了确认.结果表明;该反应是多通道多步骤的放热反应,分别可以在单重态和三重态势能面上进行,OBrO与NO通过加成及加成-消除机理分别形成产物BrONO₂和BrO+NO₂,从能量上看,形成离解产物的通道更容易进行.     

2-氨基-5巯基-1,3,4-噻二唑异构化反应机理的量子化学研究

用密度泛函理论(DFT)中的B3LYP方法,采取6-31+G* *基组对2-氨基-5巯基-1,3,4-噻二唑(简称AMT)的异构化反应机理进行了量子化学研究,全参数优化了异构化过程中反应物、产物的几何构型,找出了异构化途径中的过渡态,并通过振动分析加以确认,同时进行零点能校正.研究结果表明,异构化过程存在六种不同的异构化通道,有六个过渡态,相对而言, A→C之间的异构化反应最易发生,C是最稳定的异构化产物.     

锰离子参与的类Fenton反应的HPLC和ESR波谱研究

利用自旋捕捉-ESR技术及芳环羟基化反应-高效液相色谱(HPLC)法两种方法研究了Mn^2＋参与的类Fenton反应. 两种方法均检测到Mn^2＋与H₂O₂反应产生•OH. 建立了HPLC-荧光检测器对•OH的高灵敏快速检测方法. 检测了超氧化物歧化酶以及几种Mn^2＋配体对产生•OH的影响. 结果显示, Mn^2＋与H₂O₂反应可以发生类Fenton反应, 产生•OH. 这一现象可能是Mn^2＋引起生物体内氧化损伤的重要原因.