Theoretical Studies On The Mechanism Of The Reactions Of Halogen-compounds With Chlone Atom

Chlorine atom and halogen-compounds play important roles in the chlorination of industrial and incineration process of danger halogenated waste. These species will not only damage the ozone layer in the atmosphere but also trigger the greenhouse effect. Such microscopic studies of the mechanism and dynamic nature of these reactions have significant meanings for us to seek to protect the atmospheric environment. Chemical reaction rate constant research and determination have been to focuses of research in the chemical area. To realize forecast the chemical reaction rate constant under different conditions in theory is at the forefront of theoretical chemistry.In this thesis the mechanism of the reactions of Cl with CH₂ICl, CH₃OCl and halogenated acetones in atmosphere have been studied by using ab initio in program Gaussian03. Information of potential energy surface, including the optimized geometries of reactants, products, complexes and transition states together with the harmonic vibration frequencies analysis, reaction barrier and the reaction enthalpy of equilibrium geometries have been obtained. Under the same level, transition states have been set as the starting point and have been calculated the minimum energy path (MEP) through the intrinsic reaction coordinate (IRC). Further confirmation of the single-point energies are completed under the high-level MC-QCISD and QCISD. To the reaction of Cl with halogenated acetones CH₃COCCl₂X (X = F, Cl and Br), rate constants have been calculated by program POLYRATE 9.1. The electronic electrostatic potential for the reactant atoms and molecules have also been analyzed.To the reaction of Cl with CH₂ICl, six possible reaction channels have been calculated. Two complexes and six transition states have been found out. The results show that the reaction channel of Cl abstraction is the major channel of six channels and others are minor channels. To the reaction of Cl with CH₃OCl, four possible reaction channels have been calculated. One complex and four transition states have been found out. The results show that the reaction channel of H abstraction is the major channel of four channels and others are minor channels. To the reaction of Cl with halogenated acetones CH₃COCCl₂X (X = F, Cl and Br), three reactions have been compared. The results show that the reaction barrier of the reaction of Cl with CH₃COCCl₂Br was the lowest and easy to happen. The geometric structure, frequencies and the rate constants through the theoretical calculation are in good agreement with the available experimental value. It further verify the reliability of the theoretical results and provide a good estimate for the kinetics of the reactions in the other temperature range that experiments have not yet been able to.