【作者】 朱元强；

【导师】 李来才；

【作者基本信息】 四川师范大学 ， 材料学， 2005， 硕士

【摘要】 本文用量子化学计算程序及较大基组,研究了甲醛及甲酰基自由基与自由基或活性小分子间在室温条件下的微观反应机理,主要研究了以下体系: 1.HCO自由基和HO₂自由基的反应; 2.HCHO和HO₂、OH、H自由基的反应; 3.HCHO和NO₂的反应。 我们用密度泛函理论的B3LYP方法全参数优化了各反应体系中的反应物、中间体、过渡态及产物的几何构型,通过振动分析和内禀反应坐标（IRC）计算确定了各反应可能的中间体和过渡态。我们想通过对这三个反应体系反应机理的研究,弄清楚标题化合物在大气循环过程中各反应的复杂过程,以便找到各反应的主要反应通道和主要产物,为实验工作者和大气净化处理提供理论依据。因为我们所研究的反应体系均为小分子反应,所以我们对有些反应采用了最近发展起来的Gaussian-3（G3）方法进行研究。研究结果表明:对HCO自由基和HO₂自由基反应,我们找到了六条不同的放热反应通道,主反应通道为HCO+HO₂→TS2→IM2→HCHO+O₂,而其它几条通道都会首先生成一个非常稳定的中间体,放出大量的热,以促进反应的发生,所以各条通道间会相互竞争。生成的甲醛分子非常稳定,很难进一步裂解,但反应可通过中间产物HCO更多还原

【Abstract】 In the first section of this thesis, the mechanisms of reactions between formaldehyde or formacyl radical and active radicals or small molecules has been studied by the quantum-chemical calculation programs with big basis sets at the room temperatures. In this section, we study the following three reaction systems:1. Reaction of the HCO radical and HO₂ radical;2. Reaction of the HCHO and HO₂, OH, H radicals;3. Reaction of the HCHO and HO₂ molecule.We optimize the geometries of all stationary points in the systems by using density functional theory （DFT） B3LYP method. Our purpose of this study is to make clear the complex processes of reactions involving formaldehyde or formacyl radical and to find out the main channels and the main products. It is theoretically helpful for the experimental scientists and atmospherical purification. Gaussian-3 （G3）, which has been developed recently and regarded as one of the most accurate methods, is employed in this thesis. The results of the study are: the HCO+HO₂ reaction has six possible exothermic channels, the major one of whichis HC0+HO,-*TS2—IM2—HCHO+Oz The other channels will compete with the major one by forming a very stable intermediate firstly. In the HCH0+H02 reaction, there are four possible endothermic channels, and the main one is HCHO+ HQ,—IM1—TS1—IM2+H2QI-’TS2-mA—HA-KXH1. Products such as H202, CO and H atom are easier to get formed than the others. The HCHO+HO reaction has three possible exothermic channels, and the main one is HCHO+OH—TM9—TS13—IM2（HCO）+H2. The HCHO+H reaction has three possible exothermic channels, and the main channel is HCHO+H—TS19-*IM2 （HCO） +H2. The HCHO+NO2 reaction has three possible exothermic channels, and the main one is O(WKV^IMl-*TSl-*IM2-^IM6+C0—TS4+C0-H0N0+C0.In the second section of this thesis, we study the behavior of atmorspheric chemistry of oxidant of CH3CHF2 （R152a）, which is an environmental friendly replacement of CFC s. When R152a reacts with OH radical, there are organic peroxy radicals formed such as CH3CFA. Moreover, peroxy radicals are the main products when the organic compounds oxidated by oxidatants at the presence of light. The reactions between organic peroxy radicals and other chemicals are one of the most important chemical circulations of the photochemical air pollution. For above reasons, we study the mechanism of the reaction between CH3CF202 and H02radical, in which, we find two possible reaction channels, of which the main one is OtCFA+HQj—IM1—TS1—CHCFjOOH+a.All formaldehyde^ formacyl radical and organic peroxy radicals play an important part in the chemical circulations and will affect human health as well as environment. At present, the study of the chemical behavior of peroxy radicals is the focuses in atmospherical field. The results can contribute to the enrichment of the database of this field.更多还原