【作者】 贾秀娟；

【导师】 王荣顺；

【作者基本信息】 东北师范大学 ， 物理化学， 2010， 博士

【摘要】 卤代甲基自由基（例如CH₂F, CH₂Cl和CH₂Br）是卤代烃或者包含卤素的废料燃烧中产生的重要中间体,在燃烧及大气化学中起着举足轻重的作用。氯氟烷（HCFCs）和氢氟醚（HFEs）与CFCs具有相似的物理化学性质,曾被作为CFCs的第一代和第三代替代物已经在诸多工业领域得到应用。为了更好的评价氟氯烷和氢氟醚对大气环境的影响,确定它们在同温层中的大气寿命是很有必要的。因此,深入研究它们的反应机理和动力学行为,对进一步揭示它们对环境的影响及其大气寿命,对控制环境污染等方面有着重要的意义。本论文利用从头算和密度泛函方法研究了卤代甲基自由基（CH₂Br、CHBrCl和CH₂I）、卤代烷（CH₂ClF和C2H5I）和氢氟醚（CF3OCHFCF3）与大气中活泼自由基和原子反应的微观机理,并在所得的反应势能面基础上,对卤代烷和氢氟醚的系列反应进行了动力学性质的计算。对该类反应的速率常数、产物分支比及其对温度的依赖关系做出了可靠的理论预测,从而为进一步研究和利用这些反应提供了理论依据。本论文的主要结果有:1. CH₂Br/CHBrCl + NO2反应机理的理论研究:1)对于CH₂Br + NO2反应,CH₂Br中的C原子可无能垒的进攻NO2中的O原子形成初始络合物H₂BrCONO-trans和H₂BrCONO-cis。从H₂BrCONO-trans出发,可生成两个主要产物CH₂O + BrNO和CHBrO + HNO。2)对于CHBrCl + NO2反应,可得到三种主要产物CHClO + BrNO、CHBrO + ClNO和CBrClO + HNO。在这三种产物中,CHClO + BrNO是最主要产物,CHBrO + ClNO和CBrClO + HNO分别是第二和第三可行的产物。3) CH₂Br + NO2和CHBrCl + NO2势能面很相似。对于这两个反应来说,三重态势能面由于存在高位垒,所以很难进行,可以忽略。2.对于CH₂I + NO2反应机理的理论研究:1) CH₂I中的C原子可无能垒的进攻NO2中的不用原子（N原子或O原子）形成初始络合物H₂ICNO2、H₂ICONO-trans和H₂ICONO-cis。2)从H₂ICONO-trans出发,可生成两个主要的产物CH₂O + INO、CHIO + HNO和一个二级产物CH₂O + I + NO。CH₂O + INO是最主要产物,CHIO + HNO是第二可行的产物。我们的计算得到的主要产物与实验上观测到的CH₂I + NO2反应的结论相一致。3) CH₂I + NO2和CH₂Br + NO2势能面很相似。对于这两个反应来说,三重态势能面由于存在高位垒,所以很难进行,可以忽略。通过电负性方面和能垒方面的分析,我们预测CH₂I + NO2反应比CH₂Br + NO2反应快与实验结果相一致。3.利用双水平直接动力学方法系统研究了Cl + CH₂FCl反应。在QCISD（T）/6-311++G（d, p）//MP2/6-311G（d, p）水平下获得了反应的势能面信息。反应共有三条反应通道,即H-提取、Cl-提取和F-提取。计算得到的势能垒值表明,H提取通道为主要反应通道,生成产物CHFCl + HCl。在220-3000 K温度范围内计算了三条通道的结合小曲率隧道效应的正则变分过渡态速率常数。计算值和已有的实验值符合的很好。总反应速率的三参数Arrheniun表达式,（单位:cm3 molecule-1 s-1）: k（T） = 1.48×10-17T2.04exp（-913.91/T）。4.运用双水平直接动力学方法研究了多通道反应C2H5I + Cl。势能面是采用MP2方法结合对C, H和Cl采用6-311++G（d, p）基组,对于I采用三-ζ包含有效核赝势的系统收敛基组（aug-cc-pVTZ-PP）得到的。再利用CCSD（T）和QCISD（T）方法对反应体系中的所有稳定点和MEP上选取的部分点进行了高水平能量校正。该反应,共有四条反应通道,计算了三条氢提取反应通道和相应的氘取代反应通道的速率常数以及反应速率分支比。温度在1200K以下时,亚甲基氢提取通道是主要的。但是当温度升高时,甲基氢提取通道开始具有竞争性。总反应在220-1500K温度范围内的速率常数三参数表达式为k（T） = 2.33×10-16 T 1.83 exp（-185.01/T） cm3 molecule-1 s-1。氘取代同位素效应（KIE）在低温区间较为重要,而在高温区间影响不大。5.运用双水平直接动力学方法研究CF3CHFOCF3 （HFE-227 mc） + OH以及CF3CHFOCF3 + Cl反应的反应机制,所有稳定点的几何构型和频率以及最小能量路径。利用同构反应（R7.3a-R7.4c）,在理论上估算了CF3CHFOCF3和CF3CFOCF3自由基的标准生成焓数据。计算的这两个反应的包含小曲率隧道效应校正的改进的正则变分过渡态速率常数（ICVT/SCT）与相应的可利用的实验值吻合的很好。速率常数计算结果表明,对于CF3CHFOCF3 + Cl反应,速率常数是正温度效应,对于CF3CHFOCF3 + OH,在低温区域（220-250 K）表现为负温度效应。两个反应速率的三参数Arrheniun表达式分别为,（单位:cm3 molecule-1 s-1）: k1 = 2.87×10-21 T 2.80 exp （-1328.60/T） k2 = 3.26×10-16 T 1.65exp （-4642.76/T）。更多还原

【Abstract】 Halogenated Methyl （such as CH₂F, CH₂Cl and CH₂Br） is the important intermediates derives from the combustion of halogenated methyl or waste containing halogen, which plays a significant role in the combustion chemistry and atmospheric chemistry.Hydrochlorofluorocarbons （HCFCs） and hydrofluoroethers （HFEs） have the similar physical chemistry property of CFCs. They have been the first and third generation alternatuvel compounds to CFCs and are used in various industrial applications. It is necessary to know the atmospheric lifetime in order to better assess the atmospheric and environmental impact of HCFCs and HFEs. Therefore, detailed investigations on the mechanisms and kinetics of those reactions are very important to control atmospheric pollutions.Using ab initio and density function theory （DFT） chemistry methods, we studied the the detailed mechanisms and pathways of halogenated methyl （CH₂Br、CHBrCl and CH₂I）, haloalkanes(（CH₂ClF and C2H5I）, and hydrofluoroethers（CF3OCHFCF3） with active radicals and atoms reactions. Furthermore, based on the potential energy surface （PES） obtained, kinetics properties for series reactions of haloalkane and hydrofluoroethers. Theoretical prediction of the rate constants, the temperature dependence of branching ratios are provided for further studying and using these reactions experimentally. The important and valuable results in this thesis are summarized as follows:1. Theoretical studies on the mechanisms of CH₂Br/CHBrCl+NO2 reactions: （1） For the CH₂Br + NO2 reaction, the C atom of CH₂Br radical can barrierlessly attack the O atom of NO2 to form the initial radical-molecular adduct H₂BrCONO-trans and H₂BrCONO-cis. Two primary products P1 （CH₂O + BrNO） and P2 （CHBrO + HNO） are obtained. （2） For the CHBrCl + NO2 reaction, three kinds of primary products P1 （CHClO + BrNO）, P2 （CHBrO + ClNO） and P3 （CBrClO + HNO） should be observed. Among these products, P1 is the most favorable product while P2 and P3 are second and third feasible products, respectively. （3） The PES features of the CH₂Br + NO2 and CHBrCl + NO2 reactions are similar. The triplet pathways have much less competitive abilities for both reactions and can thus be neglected.2. For the theoretical studies on the mechanisms CH₂I + NO2 reaction: （1） With the different atom （N or O atom） in NO2 approaching to C atom, different initial intermediates are formed, H₂ICNO2, H₂ICONO-trans, and H₂ICONO-cis, respectively. （2） Starting from H₂ICONO-trans, two primary products CH₂O + INO and CHIO + HNO, and one secondary product CH₂O + I + NO should be observed. CH₂O + INO may be the most feasible product with a largest yield, and CHIO + HNO may be the second favorable products. Our results agree well with the experimental observation for CH₂I + NO2 reaction. （3） The PES features of the CH₂I + NO2 and CH₂Br + NO2 reactions are similar. The triplet pathways have much less competitive abilities for both reactions and can thus be neglected. From electronegativity and barrier height analysis, we predicted that reaction CH₂I + NO2 is faster than CH₂Br + NO2, which is in accord with the experimental results. 3. The reaction Cl + CH₂FCl→products have been studied by dual-level direct dynamics methods. The potential energy surface information is obtained at the QCISD（T）/6-311++G（d, p）//MP2/6-311G（d, p） level. Three reaction channels are identified, i.e., H-abstraction, Cl-abstraction, and F-abstraction. The calculated potential barriers show that major pathway is H-abstraction channel leading to the products, CHFCl + HCl. For each individual reaction channel, the theoretical rate constants in the temperature region of 220-3000 K are calculated by the canonical variational transition state theory （CVT） with the small-curvature tunneling correction （SCT）. The calculated total rate constants of these reactions are in good agreement with the corresponding experimental values. Three-parameter rate constant expressions of the whole reaction is given as follows: （in unit of cm3 molecule-1 s-1） k（T） = 1.48×10-17T2.04exp（-913.91/T）.4. The multichannel reactions C2H5I + Cl are studied by a dual-level direct kinetics method. The potential energy surface information is obtained at the MP2 level with 6-311++G（d, p） basis set for C, H and Cl and aug-cc-pVTZ-PP basis set for I atom. The higher-level energies for the stationary points and extra points along the minimum energy path are refined at the CCSD（T） and QCISD（T） levels. For the title reaction, four reaction channels are identified. The rate constants and the branching ratios for three hydrogen abstraction reaction channels and the corresponding deuterium substitution reaction channels are calculated by the ICVT incorporating SCT correction. The contribution of H-abstraction from -CH₂- group channel is important below 1200 K. However, H-abstraction from -CH3 group channel is competitive at higher temperatures. The three parameter expression for the total reaction within 220-1500 K is k（T） = 2.33×10-16 T 1.83 exp（-185.01/T） cm3 molecule-1 s-1. The deuterium KIE is significant in the low-temperature range, but is less important in the high-temperature region.5. The geometries, frequencies of all the stationary points, the minimum energy paths （MEPs）, and reaction mechanisms of CF3CHFOCF3 + OH and CF3CHFOCF3 + Cl reactions. Standard enthalpies of formation of CF3CHFOCF3 and CF3CFOCF3 radical are estimated theoretically using group-balanced isodesmic reactions （R7.3a-R7.4c）. The rate constants of the hydrogen abstraction reactions calculated by improved canonical variational transition state theory with small-curvature tunneling （ICVT/SCT） correction are consistent with the available experimental values. The rate constant calculations show that the rate constants of CF3CHFOCF3 + Cl reaction have positive temperature dependence. For CF3CHFOCF3 + OH reaction, at lower temperature （220-250 K）, the rate constants have negative temperature effect. The three-parameter Arrhenius expressions are as follows （in units of cm3 molecule-1 s-1）: k1 = 2.87×10-21 T 2.80 exp （-1328.60/T） k2 = 3.26×10-16 T 1.65exp （-4642.76/T）.更多还原