The Reaction Mechanism Of C 2 H 5 OO With OH And The Theoretical Study Of Water/sulfuric Catalytic Decomposition Of Trioxide C 2 H 5 O 3 H

Peroxy radicals(RO2)are the most critical intermediate in the chemistry of atmosphere,with a global production predominantly owing to the oxidations of hydrocarbons by hydroxyl radical(OH).The peroxy radicals are characterized by excess internal energies and therefore easily react with atmospheric trace gas species.Subsequent decay processes of peroxy radicals strongly depend on the air quality.In the remote atmosphere,that is in the presence of low NOx concentrations,one of the most important degradation processes for the RO2 radical is the reaction with OH radical.The detailed reaction mechanism of C2H5O2 with OH radicals and water as well as sulphuric acid assisted decomposion of C2H5O3H teroxide have been investigated using Density Function Theory(DFT)and high-level ab initio methodologies(CCSD).The thesis includes four chapters.In chapter 1,the formation of peroxy radicals and its research conditions are introduced theoretically and experimentally.In chapter 2,this chapter presents the theory of quantum chemistry and computational methods in our study.In chapter 3,the mechanisms of the C2H5O2 + OH reaction are investigated on both the singlet and triplet potential energy surfaces(PESs).A comprehensive property of the C2H5O3H complex is calculated.The enthalpies of formation of some stationary points are predicted using the atomization energy method at the CBS-QB3,G4 and G4MP2 levels of theory.In chapter 4,we investigate the reaction activation energy of the decomposition of teroxide C2H5O3H catalyzed by water and sulphuric acid molecules.The main conclusions are drawn as follows:(1)A comprehensive theoretical study on the bimolecular reaction of C2H5O2 with OH radicals was performed at the CCSD(T)/6-311++G(2df,2p)//B3LYP/6-311+G(d,p)level of theory.The calculation results show that C2H5O2 + OH reaction proceeds on both the singlet and triplet potential energy surfaces(PESs).On the singlet PES,the favorable pathway is the addition of OH radical to the terminal oxygen atom of C2H5O2 radical,leading to the formation of trioxide C2H5O3H with a barrierless process.Then,the trioxide directly decomposes to the products C2H5O and HO2 radicals.On the triplet PES,the predominant pathways are ? and ? hydrogen atom abstraction of C2H5O2 radical by OH radical-forming products 3CH3CHO2 + H2O and 3CH2CH2O2 + H2O,and the corresponding barriers are 12.02(3TS8)and 19.19(3TS9)kJ-mol-1,respectively.In addition,the comprehensive properties of trioxide C2H5O3H were investigated for the first time.The results indicate that the trioxide complex RC1 can exist stably in the atmosphere owing to a significantly large and negative enthalpy of formation(-118.44 kJ mol-1)as well as a high first excitation energy(5.94 eV).(2)In the study of the reaction mechanism of C2H5O2 and OH radicals,the energyies of decomposition of the teroxide C2H5O3H are high on the singlet PES,and it looks impossible to occure under atmospheric conditions.Considering to the high concentration of water and sulphuric acid in the atmosphere,the reaction energies for the formation of P1(1CH3CH02 + H2O),P2(C2H5OH + 1O2)and P7(1CH3CHO + H2O2)catalyzed by water and sulphuric acid are investigated at CCSD(T)/6-311++G(2df,2p)//B3LYP/6-311+G(d,p)level of theory.We designed following four catalyzed models:(1)Polarizable continuum model:reactions in water solvent(Model 1).(2)Hydrogen transfer bridge:the direct participation of water or sulphuric acid molecules in the reaction pathways(Model 2).(3)Microsolvation medium:water molecules interact with reactants through hydrogen bond(Model 3).(4)A combination of hydrogen transfer bridge and microsolvation medium(Model 4).The result shows that the energy for the formation of 1CH3CHO2 + H2O is increased,and the energies for the formation of C2H5OH + 1O2 and 1CH3CHO + H2O2 are decreased in Model 1 compared with those of in gas.The formation of C2h5OH + 1O2 is catalyzed by water molecules in Model 2,while the formations of 1CH3CHO2 + H2O and ICH3CHO+ H2O2 are not catalyzed at all.The activation energy for the formation of C2H5OH +1O2 is decreased by 123.61 kJ·mol-1 when it is catalyzed by water and sulphuric acid simultaneously in Model 2.All of three channels are slightly catalyzed by water molecules in Model 3.