Theoretical Study On The Reaction Mechanism Of Criegee Intermediate RCHOO (R=H,CH₃) And NO_x (x=1,2)

Criegee intermediate,originated from the ozonolysis reaction of alkene,is a kind of important species in the troposphere for its high chemical activity.They would have crucial effect on the formations of photochemical smog,organic haze and secondary organic aerosols,which may result in a series of environmental problems.Criegee intermediates could produce OH radical by the isomerization reactions.Alternatively,it would react with some typical species?such as SO2,NOx,and HOx?and increase the concentration of H2SO4?including sulfate?and HNO3?including nitrate?in the atmosphere.So it is very necessary to research the mechanisms,thermodynamical and kinetical properties for the reactions between Criegee intermediates and some typical species?such as SO2,NOx,and HOx?in atmosphere.These results would not only help to understand the formation mechanisms of acid rain and secondary organic aerosols,but also give scientific instructions for the elimination of atmosphere pollutants.This paper have investigated the mechanism and kinetics for the reactions of Criegee intermediate RCHOO?R=H,CH₃?with nitrogen compounds?NOx?x = 1,2??in details by using the density functional theory?DFT?.NO,shows a wide range of nitrogen oxides and NOx?x =1,2?shows nitrogen of NO and N02 in this thesis.The main contents and conclusions in this paper are listed as follows:Chapter one summarized the research results on the generation and hazard of the Criegee intermediate and nitrogenous compounds?NOx?x = 1,2??in recent years.For Criegee intermediate and nitrogenous compounds NOx the current research situation to determine the reaction system of this article mainly research RCHOO?R=H,CH₃?+ NOx?NOx?x = 1,2??.Chapter two introduced about the quantum chemistry theory and computational methods involving in the paper.In chapter three,the mechanism for the reaction between RCHOO?R=H,CH₃?and NO are studied at CCSD?T?/aug-cc-pVTZ//M06-2X/cc-pVDZ level.We use the transition state theory?TST?to calculate the rate constant of the cycloaddition and C-N addition reaction in 200-500K.Results show that the addition and oxidation mechanism mainly included cycloaddition,C-N addition,N-O addition,and C-O addition.Meanwhile,the cycloaddition reaction produce is NO2 + HCHO.The apparent activation energy is 26.08 kJ· mol-1 and The C-N addition reaction produce is ONCH2OO.The apparent activation energy is 14.37 kJ· mol-1.However,the cycloaddition and C-N addition there may be some competition relations.The C-N addition has some advantages.Moreover,in 298.15K we predicted the syn-CH₃CUOO + NO and anti-CH₃CHOO + NO addition reaction of C-N addition channel?R-2b,R-2c?rate constants were 1.62 × 10-15 and 3.38 × 10-15 cm3· molecule-1· s-1.In additional,the reactivity of addition and oxidation reaction of anti-CH₃CHOO is higher than the syn-CH₃CHOO.In chapter four,the mechanism of RCHOO?R=H,CH₃?+ NO2 reaction is studied at CCSD?T?/aug-cc-pVTZ//M06-2X/cc-pVDZ level.The influence of the methyl substitution on the reactivity was discussed.The results show that the title reaction could take place through three channels addition-decomposition,oxidative H-transfer and hydrogen abstraction Therein,the oxidative H-transfer reaction which mainly produce the RCO + HNO3,is the favorable pathway.The apparent activation energy is 40.51 kJ· mol-1 and release energy is 235.04 kJ· mol-1.Moreover,the methyl substituent will leads to the increase of the electropositivity on a-C and decrease of the electronegativity on terminal O,which is advantageous to proceed the addition-decomposition and oxidation-hydrogen transfer reaction.However,the reactivity of the addition-decomposition reaction reduced because of the prominent steric effect in syn-CH₃CHOO.