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1.
采用G3MP2B3方法研究了氧负离子与乙腈反应的势能剖面.在(U)B3LYP/6-31+G(d,p)理论水平下分别优化了该反应势能面上反应物、产物、中间体和过渡态的分子结构,采用G3MP2B3方法校正了这些关键点的能量. 势能面上的各个反应路径均通过针对过渡态的內禀反应坐标理论计算加以确定. 分别考察了四个可能的热力学产物通道,即质子转移、氢原子转移、H2+转移和双分子亲核取代反应途径. 其中,经H2+转移生成H2O的反应通道为该反应的主要产物通道.  相似文献   

2.
利用CCSD(T)和MP2的理论方法研究了OH与臭氧反应,并考虑大气中水分子的影响.理论计算探索了OH与臭氧反应的两个反应通道,计算出的能垒与以前的实验和理论符合得较好.当水分子被加入时,反应变得更加复杂,发现了六个反应通道,更重要的是反应能垒降低约4.18 kJ/mol.为了评估这些过程在大气化学中的重要作用,用过渡态理论计算了反应速率.计算结果表明,在298 K,对于没有水参加反应的反应速率为5.16×10-14 cm3/(molecule s)与实验一致.  相似文献   

3.
本文利用时间切片离子速度成像技术对AlO分子在193 nm下的光解反应动力学进行了研究. 实验通过产物Al+的离子速度和角度分布分析,发现了两个光解离反应通道,分别为中性AlO分子的单光子解离生成产物Al(2Pu)+O(3Pg)的通道,和AlO分子吸收两个光子电离产生AlO+进而解离生成产物为Al+(1Sg)+O(3Pg)的反应通道. 每一个解离通道包括了AlO(v=0∽2)振动态的贡献,其中中性解离反应通道与离子解离反应通道相比,产物的各向异性参数对AlO的振动态依赖更大.  相似文献   

4.
在两个耦合的势能面12A′和22A′上对N+ND反应进行了非绝热量子动力学研究. 计算了N+ND→N2+D反应和N′+ND→N′D+N反应在5 meV~1.0 eV碰撞能的反应几率和积分截面. 结果发现N+ND→N2+D反应是N+ND反应的主要反应通道.另外,计算了N+ND→N2+D 反应的速率常数.  相似文献   

5.
利用同步辐射光电离质谱结合理论计算, 研究了异亮氨酸的真空紫外光诱导电离解离.在光子能量为13 eV的质谱中探测到了m/z=86、75、74、69、57、46、45、44、41、30、28、18的碎片离子.对于异亮氨酸的主要碎片离子为:C5H12N+ (m/z=86)、C2H5NO4+ (m/z=75)、C5H9+ (m/z=69)、C4H9+(m/z=57)和CH4N+(m/z=30).由光电离效率曲线得到出现势分别为:8.84±0.07、9.25±0.06、10.20±0.12、9.25±0.10、11.05±0.07 eV.结合量化理论计算(B3LYP/6-31++G(d,p)),详细给出了它们可能的生成路径.这些解离通道包括简单的键断裂反应和涉及中间体、过渡态的反应,实验值和理论计算的离子出现能或势垒一致.  相似文献   

6.
基于精确的势能面,研究D+OD+反应在0.0~1.0 eV碰撞能范围内的量子动力学. 用CS近似(centrifugal sudden approx-imation)的含时波包方法研究吸热的抽取反应通道(D+OD+→ O+D2+)和热中性的交换反应通道(D+OD+→D+OD+),计算两个通道的反应几率、总积分反应截面和热速率常数. 发现在交换反应的反应路径上存在一个凸起结构. 计算的总角动量J=0时的波包分布的含时演化清楚地表明凸状结构对两个通道的动力学有非常重要的影响.  相似文献   

7.
在G2(B3LYP/MP2/CC)理论水平上研究了CH(X^2Ⅱ)自由基与氧化二氮(NNO)分子的反应。计算了反应体系的最低二重态势能面上各驻点的构型参数、振动频率和能量,揭示了此反应存在的两种机理和六个通道。基中HC和NNO复合,生成中间体HC(N)NO,解离得到产物HCN+NO,这是最主要的通道之一;HC插入NO键,克服38.9kJ/mol的势垒,产生富能的中间体HC(O)NN,预测了五个反应通道,其中主要反应通道为:NN+HCO.  相似文献   

8.
利用abinitio方法对CH3CH2+O(3P)反应进行了理论研究,在MP2/6311+G(d,p)水平上优化得到了反应途径上的反应物、中间体、过渡态和产物的几何构型和谐振频率,并在QCISD(T)/6311+G(d,p)水平上进行单点能计算.计算结果表明:CH2O+CH3、CH3CHO+H和CH2CH2+OH是主要反应产物,其中CH2O+CH3主要来自反应通道A1:(R)→IM1→TS3→(A),CH3CHO+H主要来自反应通道B1:(R)→IM1→TS4→(B),CH2CH2+OH主要来自直接抽提反应通道C1和C2:(R)→TS1(TS2)→(C).计算结果同时表明该反应生成CO的通道能垒是非常高的,CO应该不是主要产物.  相似文献   

9.
用CCSD(T)//MP2/6-31G*方法研究了单重态二甲基亚烷基硅烯与乙烯生成硅杂双环化合物环加成反应的机理,根据该反应的势能面可以预言,该反应只有一条主反应通道. 该主反应通道所呈现的反应规律为:二甲基亚烷基硅烯中Si原子的3p空轨道与乙烯中的π轨道形成了π→p授受键,生成三元环中间体(INT1);扩环作用使INT1异构化为四元环硅烯(P2);P2中Si原子的sp3杂化使P2进一步与乙烯结合生成了硅杂双环化合物.  相似文献   

10.
用G3B3//B3LYP/6-311G(d,p)方法计算了戊二烯基与氧分子反应的势能面.计算结果显示,反应的第一步为戊二烯基与氧分子结合形成两种过氧化加成物,过氧基分别连结在末端C1位置和中间C3位置.在反应的第二步,两种过氧化加成物分别发生一系列氢转移异构化反应和成环异构化反应.最后,这些氢转移异构体和环化异构体分别经过单分子分解通道,生成不饱和醛酮和羟基.共计算了20个稳定态和14个过渡态的结构和能量,通过比较各反应通道的能垒和反应热,提出以C2H3O和C3H4O为最终产物的通道可能是整个反应的主要通道.此外,计算结果还表明一些过C5H7O2自由基可能作为反应体系的长寿命中间体而存在,这与Zils等人的实验观测结果一致.  相似文献   

11.
A detailed computational study has been performed at the QCISD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p) level for the NCO with CH3 reaction by constructing singlet and triplet potential energy surfaces (PES). The results show that the title reaction is more favorable for the singlet PES than the triplet PES. On the singlet PES, the dominant channel is the barrierless addition of the O or N atom to the C atom of the methyl group to form CH3NCO (IM1) and CH3OCN (IM2). On the triplet PES, the favorable channel is the barrierless addition of the N atom to the C atom of the methyl group to form an intermediate CH3NCO (3IM2), which then undergoes a N–C bond scission process to give out CH3N + CO.  相似文献   

12.
路广霞  张辉  张国英  梁婷  李丹  朱圣龙 《物理学报》2011,60(11):117101-117101
采用基于密度泛函理论的赝势平面波第一性原理方法,研究了LiNH2缺陷及其掺杂原子交互作用对其释氢影响.通过对其进行优化求得它们的局域最稳定结构并计算了含间隙H原子缺陷的LiNH2及其掺杂合金的结合能、间隙缺陷形成能、态密度和电荷布居.结果表明: 系统结合能不能反映LiNH2及其掺杂合金的释氢性质;平衡时,LiNH2中有一定的间隙氢原子存在,Mg,Ti掺杂使形成能大大降低,大大增大了间隙氢的浓度. 间隙H原子在带隙引入了缺陷能级使带隙大大减小,提高释氢能力.间隙H原子导致[NH2]-中N-H原子间相互作用减弱,容易释氢.间隙H与[NH2]-中N存在共价作用,可以解释LiNH2释氢反应中NH3的放出.当存在掺杂时,N-H键的键强不均衡,部分较弱,部分较强,较弱的N-H键中H容易放出. 关键词: 储氢材料 第一性原理 缺陷 释氢机理  相似文献   

13.
The hydrolysis mechanism of glycylserine in the presence of Zn2+ was theoretically studied by means of density functional theory calculations. Two possible reaction mechanisms are proposed for the hydrolysis reaction: (1) the first one involves a stepwise reaction with an initial attack of the serine –OH to the amide carbonyl group through a general base catalysis of a water molecule, which undergoes to a proton transfer to the carboxylate group to give a cyclic intermediate. Its further rearrangement finally forms an ester that hydrolyses to yield products. (2) The second mechanism involves a general base catalysis by the carboxylate group for the water attack to the amide carbonyl group to generate a tetrahedral intermediate. Upon comparison of both mechanisms, it is observed that the former is favoured; furthermore, its first step is the rate-limiting step in a bicyclic asynchronous transition state with evolution of 86% in C(1)–O(2) bond. The crucial role of Zn2+ in this hydrolysis process can be rationalised in terms of the inductive effect and the formation of a rigid structure that increases the electrophilicity of the amide carbonyl group. The calculations presented in this report are in good agreement with reported values for the activation barrier.  相似文献   

14.
The intramolecular asymmetric Michael addition reaction catalyzed by imidazolidinone is investigated using the density functional theory calculations. The details of the reaction mechanism, potential energy surfaces, and the influence of the acid additive are investigated. The reaction process includes two stages. The first stage is Michael addition, in which the enamine complex is created and then the Michael addition is carried out. The second stage is a product separation stage which includes an enol‐keto tautomerization and a two‐step hydrolysis. The enantioselectivity is controlled by the Michael addition step which involves a new carbon–carbon bond formation. The calculation results provide a general model which may explain the mechanism and enantioselectivity of the title reaction. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

15.
The electronegativity was defined by Pauling1 as a measure of the power of an atom in the molecule to attract electrons to itself. This concept of electronegativity has undergone radical changes. Recent calculations of electronegativity show2,3 that it is a complex quantity including an important atomic term depending on the charge and hybridization of the atom, and a molecular term depending on the length and the nature of the bonds in the molecule. In a molecular group of the type A-B, B is a halogen atom, say chlorine and A stands for different atoms of a subgroup of the periodic table. Since the nature of the bonds in the molecule AB and the electronegativity of halogen atom, B, is constant for a molecular group, the electronegativity, X, of atom A may be related to the dissociation energy and bond length which in its turn is related to the vibrational constant,ωe, and the reduced mass, μ, of the molecule AB.  相似文献   

16.
The intermolecular interactions in solutions of aminophenols in CCl4 are studied by the methods of IR Fourier spectroscopy. If the hydroxyl groups of aminophenol molecules occupy the ortho positions with respect to the amino groups of the molecules, the hydroxyl and amino groups are involved in intramolecular interactions with the formation of hydrogen bonds O-H...N and N-H...O. The introduction of two additional tert-butyl groups into the structure of the aminophenol molecule facilitates the formation of O-H...N bonds and impedes the formation of N-H...O bonds. The occurrence of the carbonyl group in the structure of aminophenols leads to the formation of intramolecular hydrogen bonds O-H...O=C. The introduction of the methyl groups into carbonyl-containing aminophenols transforms the O-H...O=C bond into the hydrogen bond N-H...O=C.  相似文献   

17.
This work describes the conformational behavior and the activation mechanism of timoprazole and substituted prazoles from the most stable conformation to the sulphenic acid. The stability of the conformers can be explained by the presence of hydrogen bonds, stereoelectronic effect because of the lone pair of sulfur atom and the NC and NS interactions. The first step of the Smile rearrangement is a nucleophilic addition to benzimidazole by pyridine moiety, which depends on the difference of the electron population of the atoms involved in the attack. The second step produces sulphenic acid by a concerted reaction where breaking of the S–C bond goes along with a proton migration, and is determined by the electron population of the sulfur atom. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

18.
A study has been performed on the mechanism for the Ag(I)‐catalyzed intramolecular aminofluorination of N‐arylpent‐4‐enamides with Selectfluor by means of density functional theory. According to the calculations, the whole catalytic cycle consists of a series of elementary reactions, including formation of the complex ( IMC ) of the substrate and Ag(H2O)+ (derived from the ligation of H2O to Ag(I)), oxidation of the complex IMC by Selectfluor, deprotonation, homolytic cleavage of the N–Ag(II) bond, intramolecular radical cyclization, and fluorine abstraction. It is suggested that the oxidation of the complex IMC should be the rate‐determining step and that the intramolecular radical cyclization determines the regioselectivity of the reaction. Different from that in the decarboxylative fluorination, herein, the deprotonation of the amide is initiated by Ag(II) rather than Ag(I).  相似文献   

19.
采用密度泛函理论中杂化密度泛函B3LYP/6-311G(d,p)方法,对(LiH)_n(n=1~5)团簇结构进行计算,得到最稳定构型,并计算分析其与NH_3的反应机理.对各反应的中间体和过渡态进行频率分析和内禀反应坐标(IRC)计算,以验证反应的正确性.用QCISD/6-311G(d,p)方法计算各驻点的单点能,得到能量信息.结果表明:各反应所释放H_2中的两个氢原子分别来源于NH_3和(LiH)_n(n=1~5)团簇.弱化N-H键的作用有利于反应能垒的降低,是反应脱氢的关键.LiH团簇尺寸变化对反应能垒没有太大影响.  相似文献   

20.
Reactions that occurred during the radical polymerization of styrene in the presence of ferrocene were analyzed by the B3LYP/6-31G(d, p) method of density functional theory. The formation of the Fe-C bond between the iron atom of ferrocene and polystyrene radical (R·) was found to be energetically unfavorable, and the polystyrene chain growth reaction in the coordination sphere of the iron atom by the insertion of the monomer at the Fe-C bond was characterized by a high activation energy. Conversely, the addition of R· to the ferrocene cyclopentadienyl ring occurred with the release of energy. Indications of termination-free styrene polymerization in the presence of ferrocene experimentally observed earlier were explained in terms of reversible inhibition concepts.  相似文献   

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