Theoretical Study On The Atmospheric Chemical Reactions Of Criegee Intermediates With The Participation Of Ammonia And Amines

Criegee intermediates(CIs)are key intermediates in the ozonolysis of alkenes.The reactions of CIs play a crucial role in controlling the atmospheric oxidation capacity as well as the formation of acid rain and secondary organic aerosols(SOA),which can damage human health,influence air quality and global climate.Therefore,the Criegee chemistry has sparked a great interest and attracted much attention.Ammonia and amines,abundant basic compounds in the atmosphere,can directly or indirectly participate in the reactions of CIs.The gas-phase and air-water interface reactions of CIs with amines are potential sources of nitrogen-based aerosols.Ammonia and amines can catalyze the atmospheric chemical reactions,and their catalytic effect is stronger than that of water and acidic compounds.However,the reaction mechanisms of CIs with amines and the catalytic effect of ammonia and amines to CI reactions have not been fully understood and recognized.Moreover,owing to the high reactive activity and short lifetime,the experimental studies on the reactions of CIs are still difficult and limited.Therefore,quantum chemical calculations and molecular dynamic(MD)simulations were performed to investigate the gas-phase or air-water interface reactions of CIs with amines,and the catalytic effects of ammonia and amines on the Criegee reactions.This dissertation bridges the limitations of experimental study and provides a theoretical basis for fully understanding the cycling of free radical and the formation of SOA,thereby assessing the atmospheric lifetime of CIs and improving atmospheric chemistry models.The main contents and conclusions of the dissertation are summarized in the following four aspects:1.Reaction of Criegee intermediates with formamide and its implication to atmospheric aerosolsThe reactions of CIs play an important role in the SOA formation.Previous study has shown new particle formation(NPF)can contribute to more than half of the aerosols in terms of their number concentration.The reactions of CIs with formamide(FA)in the gas-phase and at the air/water interface were investigated using quantum chemistry calculation and BornOppenheimer molecular dynamic(BOMD)simulations.The results show that the reaction mechanism of CIs with FA is similar to that with formic acid,and the formation of hydroperoxymethyl formimidate(P4)is the most favorable pathway.Moreover,the potential contribution of the products to NPF was also evaluated by means of the molecular dynamic simulations.The results indicate that the product(P4)can participate in the sulfuric acid-based NPF and water molecules are beneficial to enhance the NPF.The exploration will provide insight into the reaction of CIs with amide and the effect of the Criegee chemistry on the atmospheric aerosols.2.Study on gas phase and air-water interface reaction of Criegee intermediates with anilineOwing to the unique surface properties,aerosol droplets can provide the reaction zones and play an important role in modifying the chemical composition.In this study,the gas-phase reaction mechanism of CH3CHOO with aniline was investigated.The results show that the reaction of anti-CH3CHOO with aniline is more favorable than that of syn-CH3CHOO with aniline.Moreover,water molecules can catalyze the reactions of CH3CHOO with aniline and make the reaction of anti-CH3CHOO with aniline to be nearly a barrierless reaction.The high rate constants of the reactions of CH3CHOO with aniline indicates that these reactions are important to remove the atmospheric aniline.BOMD simulations were performed to investigate the reaction mechanism of CH3CHOO with aniline at the air-water interface.The results show that the reactivity of anti-CH3CHOO is stronger than that of syn-CH3CHOO.Moreover,the reactions follow a loop-structure mechanism or a stepwise mechanism and occur on picosecond time scale.Subsequently,the products of CH3CHOO with aniline directly dissolve into the aerosol,which can play a role in reducin g the vapor pressures and enhancing the rate of particle formation.This study will help in deep understanding the aniline removal and the involvement of Criegee chemistry in SOA formation.3.Isomerization of Criegee intermediates catalyzed by ammonia and aminesThe isomerization of CIs is an important source of OH radicals at night or in winter.In this study,quantum chemical calculations were used to investigate the mechanism of isomerization of CIs in the presence of ammonia and amines.Two different participation paths of ammonia and amines were considered and included complexation catalysis and bridgingring catalysis.The results show that CIs whose structures are similar to syn-CH3CHOO,are more prone to isomerization than CIs whose structures are similar to anti-CH3CHOO.Ammonia and amines can catalyze the isomerization of CIs.Compared to the complexation catalysis,ammonia and amines tend to go through the bridging-ring catalysis paths to promote the isomerization of CIs.Especially,the effect of amines is more prominent.Moreover,the catalytic effect of amines increases with the number of alkyl substituents.4.Reaction mechanism of Criegee intermediates and hydroxyl radicals in the presence of ammonia and amineCIs can react with OH radicals to affect the tropospheric oxidation capacity.In this study,quantum chemical calculations were carried out to investigate the mechanism for the reaction of CIs with OH radicals.A third component,such as water,ammonia,or amines,was introduced to the reaction of CIs with OH to evaluate their catalytic effect.The results show that the OH addition is the favorable channel among four channels involving cis-H abstraction,trans-H abstraction and O abstraction.The third component has a positively catalytic effect on the transH abstraction and O abstraction pathways.Moreover,the energetic results show that for the trans-H abstraction of anti-CH3CHOO and(CH3)2COO with OH,ammonia and amine exhibit more effectively catalytic ability than water.Furthermore,a new reaction mechanism was observed in the BOMD simulations.The results show it occurs simultaneously that the addition of third component to CIs and hydrogen abstraction from the third component by OH.This finding reveals that CIs can cooperate with OH radicals to synergistically degrade ammonia and amines.