Theoretical Studies On The Mechanism Of Reactions Radicals With Methyl Iodide And DMS

The reactions related with atmospheric pollution mostly involved small molecule radicals,because the very short life and very high activity of it,and the limitation of the existing experimental equipment,make it very hard to confirm the mechanism,microstructure and the evolution of it only depend on the experimental results . Thus , it requires a combination of theoretical chemistry to analysis and forecast for the research of the reactions participanted with small molecule radicals.In this thesis,the mechanism of the reactions of small molecule radicals (as Cl,OH and CH3 radicals) with methyl iodideand DMS in atmosphere has been studied by using ab initio method,optimized the geometry of the reactant,complex,products and transition states,the minimum energy path (MEP) was obtained by intrinsic reaction coordinate (IRC) theory , and analysed the electronic electrostatic potential.The results show that the reaction channel of hydrogen abstraction is the major channel of four channels in the reaction Cl with CH3I,and the others are minor channels,it is indicated that after the atom Cl replaced the atom H,the bond between the C and H become more lively by the molecular electrostatic potential topology and energy analysis.In the channels of the reaction OH and DMS,the channel of hydrogen abstraction is the major channel,and it is also the major channel in the reaction of CH3 and DMS.Atom hydrogen is easier to be attacked by the nucleophilic reagent than the carbon atom in DMS,and OH is more lively to attack the DMS than the CH3.The microcosmic mechanism of every path in the reaction can conclude the mechanism of these reactions in theory.