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用量子化学从头计算方法在MP2/6-31G(d)水平上计算了单重态的CH2与二甲醚中C-H键插入反应的过程,并在MP4/6-31G(d)水平上计算了反应物、过渡态和产物的能量。反应仅具有一个8.1kJ/mol的早期势垒,反应过程是卡宾的一个亲电-亲核过程,在插入过程中,卡宾空的p轨道和占有一对孤电子的σ轨道分别指向C-H键的H原子和C原子。 相似文献
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使用密度泛函理论B3LYP方法和6-31G(d,p)、6-31+G(d,p)、6-311G(d,p)及6-311+G(d,p)基组,分别对2-C5H10+和1-C5H10+的各种构象进行了几何构型优化,并用B3LYP/6-311G(d,p)进行了频率分析计算.计算预言1-C5H10+具有非平面构型,与以往报导的从头算计算结论相反.在两个自由基阳离子的各种构象的B3LYP几何构型上,进行了B3LYP和UMP2(full)方法的超精细偶合常数计算,得到了比以往更好的结果. 相似文献
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单重态二溴卡宾和甲醛环加成反应的量化研究 总被引:4,自引:0,他引:4
采用量子化学密度泛函理论,研究了单重态二溴卡宾和甲醛环加成反应的机理.在B3LYP/6-31G*基组水平上,优化得到了反应途径上反应物、过渡态、中间体和产物的几何构型;计算并考察了四种可能反应途径势能面上各驻点的构型参数、振动频率和能量;通过振动分析对过渡态和中间体构型进行了确认.计算结果表明,二溴卡宾和甲醛反应有四条反应通道,其中c反应通道(即0°-0°型)控制步骤的活化能仅为13.7 kJ·mol-1,反应容易进行. 相似文献
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单重态CCl2与O3反应机理的理论研究 总被引:2,自引:0,他引:2
用量子化学从头算方法,研究了单重态CCl_2与O_3反应的机理.在HF/6-31G(d)水平上用梯度解析技术全参数优化上述反应的反应物、中间体、过渡态和产物构型,MP2/6-31G(d)//HF/6-31G(d)方法计算能量.给出了有关化合物的结构数据.结果表明:CCl_2与O_3首先生成富能中间体CCl_2O_3,然后中间体裂解生成CCl_2O和O_2.该反应为强放热反应,放出的热量为516.88kJ·mol~(-1)[MP2/6-31G(d)//HF/6-31G(d)].通过内禀反应坐标(IRC)计算,获得了沿反应途径的势能剖面. 相似文献
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本文采用BHandHLYP和MPWB1K方法结合6-31+G(d,p)基组,对臭氧与丁基乙烯基醚三种同分异构体(n-Bve、i-Bve和t-Bve)的反应机理进行了研究,优化了反应势能面上各驻点的几何构型,用内禀反应坐标(IRC)计算和频率分析方法对过渡态进行了验证.结果表明,在臭氧与丁基乙烯基醚反应中,随着丁基基团空间位阻的变化,生成OH自由基的几率发生改变.臭氧与丁基乙烯基醚之间具有较高的反应活性,二者反应很容易生成较稳定的环合中间体,且为放热反应.其中臭氧化异丁基乙烯基醚的活化能最高,臭氧化正丁基乙烯基醚的活化能最低,理论计算得到的反应势垒与相应的实验值相吻合. 相似文献
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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. 相似文献
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用量子化学密度泛函理论(DFT)方法,对COS与O2的反应进行了理论研究.在UB3LYP/6—31G^*,UB3LYP/6—311++G^**水平上,优化了反应势能面上各驻点(反应物、产物、中间体和过渡态)的几何构型,在UB3LYP/6—31G^*水平上通过内禀反应坐标(IRC)计算和振动分析,对过渡态进行了确认.在CCSD(T)/6—311++G(2d,2p)水平上进行了单点能量计算,并确定了反应机理.研究结果表明,反应主要产物为CO2和SO. 相似文献
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Ab initio calculations were carried out for the reaction of adamantylideneadamantane (Ad=Ad) with Br2 and 2Br2. Geometries of the reactants, transition states, intermediates, and products were optimized at HF and B3LYP levels of theory using the 6-31G(d) basis set. Energies were also obtained using single point calculations at the MP2/6-31G(d)//HF/6-31G(d), MP2/6-31G(d)//B3LYP/6-31G(d), and B3LYP/6-31+G(d)//B3LYP/6-31G(d) levels of theory. Intrinsic reaction coordinate (IRC) calculations were performed to characterize the transition states on the potential energy surface. Only one pathway was found for the reaction of Ad=Ad with one Br2 producing a bromonium/bromide ion pair. Three mechanisms for the reaction of Ad=Ad with 2Br2 were found, leading to three different structural forms of the bromonium/Br3- ion pair. Activation energies, free energies, and enthalpies of activation along with the relative stability of products for each reaction pathway were calculated. The reaction of Ad=Ad with 2Br2 was strongly favored over the reaction with only one Br2. According to B3LYP/6-31G(d) and single point calculations at MP2, the most stable bromonium/Br3- ion pair would form spontaneously. The most stable of the three bromonium/Br3- ion pairs has a structure very similar to the observed X-ray structure. Free energies of activation and relative stabilities of reactants and products in CCl4 and CH2ClCH2Cl were also calculated with PCM using the united atom (UA0) cavity model and, in general, results similar to the gas phase were obtained. An optimized structure for the trans-1,2-dibromo product was also found at all levels of theory both in gas phase and in solution, but no transition state leading to the trans-1,2-dibromo product was obtained. 相似文献
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DFT法研究3-羟基丙烯醛的双键旋转异构反应机理 总被引:2,自引:0,他引:2
利用密度泛函理论(DFT)分别在B3LYP/6-31G**和B3LYP/6-311++G**的计算水平上优化了基态3-羟基丙烯醛分子在双键旋转异构反应过程中的平衡态以及过渡态的几何构型,分析了反应过程中键参数的变化,计算了该反应的内禀反应坐标(IRC),发现在重排反应途径上存在一个四元环骨架的中间体.通过振动分析对平衡态和过渡态进行了确认,并得到了零点能.计算结果表明,基态3-羟基丙烯醛分子的双键旋转异构反应经过两步完成,第一步反应位垒稍高,第二步反应位垒较低,存在着发生重排反应的可能性. 相似文献
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DFT study on mechanism of the classical Biginelli reaction 总被引:1,自引:0,他引:1
Jin Guang Ma Ji Ming Zhang Hal Hui Jiang Wan Yong Ma Jian Hua Zhou School of Chemical Engineering Shandong Institute of Light Industry Jinan China 《中国化学快报》2008,19(3):375-378
The condensation of benzaldehyde, urea, and ethyl acetoacetate according to the procedure described by Biginelli was investigated at the B3LYP/6-31G(d), B3LYP/6-31 +G(d,p), and B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G(d,p) levels to explore the reaction mechanism. According to the mechanism proposed by Kappe, structures of five intermediates were optimized and four transition states were found. The calculation results proved that the mechanism proposed by Kappe is right. 相似文献
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The reaction mechanism of CH2F radical with HNCO was investigated by density functional theory (DFT)at the B3LYP/6-311++G(d,p) level. The geometries of the reactants, the intermediates, the transition states and the products were optimized. The transition states were verified through the vibration analysis.The relative energies were calculated at the QCISD(T)/6-311++G**//B3LYP/6-311++G(d,p) level. Seven feasible reaction pathways of the reaction were studied. The results indicate that the pathway (5) is the most favorable to occur, so it is the main pathway of the reaction. 相似文献
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The structures and isomerization of magnesium fluorosilylenoid H2SiFMgF were investigated by ab initio molecular orbital theory. Four equilibrium structures and three isomeric transition states were located and fully optimized at the B3LYP/6-31G(d,p) and G3MP2B3 levels, respectively. Based on the B3LYP/6-31G(d,p) optimized geometries, harmonic frequencies of various structures were obtained and 29Si chemical shifts were calculated. The solvent effects were investigated by means of the polarizable continuum model using THF as a solvent at B3LYP/6-31G(d,p) level. Isomerization paths for isomers were confirmed by intrinsic reaction coordinate calculations. The calculated results show that tetrahedral structure has the lowest energy and is the most stable; tetrahedral, three-membered ring, and p-complex structures are suggested to be the experimentally detectable ones; and σ-complex structure has the highest energy and will not exist. 相似文献
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D-苯丙氨酸与Cu+(1S0, 3d10)气相反应理论研究 总被引:1,自引:0,他引:1
用量子化学密度泛函(DFT)方法研究D-苯丙氨酸与一价基态金属阳离子Cu+在气相中反应的机理. 在B3LYP/6-31G*水平上, 优化了反应包含的4个反应通道的反应物、中间体、过渡态和产物的几何构型, 并采用B3LYP/DZVP, B3LYP/[6-311+G**(C,H,O)+Lanl2dz(Cu)], B3LYP/6-311+G**, MP2/6-311+G** 等方法对各驻点进行了单点能计算. 通过对计算结果的分析, 获得了其单重态反应势能面的一般轮廓、各驻点几何构型优化参数, 明确了其反应机理. 相似文献