Typical Atmospheric Peroxy Radical Reaction Mechanism And Kinetic Theory

Peroxy radical(HO₂ and RO₂) is an important oxidant in the atmosphere,which comes mainly from the atmosphere oxyhydrogen free radical(OH) and the NO₃ free radical with carbon monoxide member,the volatile organic matter(VOC) response production.It with Cl,NO₃,the O₃ response immediate influence atmospheric ozone layer,is having the pivotal function in the atmospheric chemistry aspect.Due to the short lives of the radicals and the difficulty to obtain the pure species,the experimental research for their structures and reaction features(especially the reaction mechanisms and the dynamics) is very difficult.Therefore,more and more attentions have been focused on their theoretical researches in recent years.In this thesis,the peroxy radical(HO₂ and RO₂) atmospheric chemistry reaction and radical amplifier chemistry water effect have been investigated with the theory method.The reaction mechanism of CH₃O₂ with Cl,NO₃,O₃ and HO₂ radical reaction with NO under the presence of water in the atmosphere have been studied at the CCSD(T) / 6-311 +G(2df,2p)//B3LYP/6-311+ G(2df,2p) and CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) level.The geometries for reactants,the transition states and the products were completely optimized.All the transition states are verified by the vibration analysis and the intrinsic reaction coordinate(IRC) calculation,provide the possible reaction route of every reaction.The resuit of study CH₃O₂+Cl indicate that the attacking of the Cl atom to the end O atom of CH₃O₂ radical is the predominant initial step for the title reaction.In single state,Cl and CH₃O₂ were found to form a complex in the initial step which then decompose via 4 channels leading a variety of products among which CH₂O₂+HCl and CH₃O+OCl are dominated.In triple state,this reaction proceeds directly without forming an intermediate.Energy analysis shows that the occurrence of the reaction is dominated in the single state.At the same time, in accordance with the POLYRATE program calculated in the Criegee radical generation rate constant channel under 298 K.The dependence of the rate constants on temperature is given with a three parameters Arrhenius equation within the temperature range 200～2000K;In the singlet state potential energy surface,the reactions of CH₃O₂+NO₃ passes through nine channels to produce five products,mainly product is CH₂O₂+HNO₃,but the altogether two channels have both produced the only product methyl nitric acid fat(CH₃ONO₂)+³O₂ in the triple state of potential energy surface; The reaction of CH₃O₂+O₃ passes through five ways to produce two products,CH₃O+³O₂ is the main product.At room temperature calculated to generate the product of the rate constant.However, due to the method calculation used and the level of theory is differently,this result with already reported the experimental result is inconsistent.Therefore this work is needed in the further to clarify the discrepancy.Studying radical amplifier chemistry chain propagation reaction HO₂+NO water vapor at the CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) level.The result of study indicate that this reaction to generate the first complex HO₂-H₂O,and then the NO molecular re-attack complex to complete the three-molecular reaction.Theoretical study of the reactions HO₂-H₂O+NO mainly produces three kinds the molecules,which HNO₃+H₂O is the main product.It is creates the water effect the important reason.At the same time,calculated rate constant of the main channel under the 298 K, and the conclusions of experiments are compared.The calculated results are fully compared with the experimental values,and the results show that the DFT direct dynamics method is reliable and feasible.We successfully predicted the rate constants and activation energy for the reactions,and predicted their temperature dependence for the reactions.This research provides a useful exploration for the dynamics study on the system with peroxy radical(HO₂ and RO₂) and radical amplifier chemistry water effect.