Experimental And Theoretical Studies Of Dissociative Photoionization And Pyrolysis Of 3-methyl-2-buten-1-ol By Using Synchrotron Radiation

3-Methyl-2-buten-1-ol（MBO321）,a biogenic volatile organic compound（BVOC）,impacts the atmosphere and human health.MBO321 is also long-chain alcohol.It has been considered as a new alternative fuel.The study of the photochemical and combustion chemistry of MBO321 is an essential fundamental topic in the atmospheric environment and energy science.These studies are of great significance to its photochemical and combustion chemistry.However,there are minimal experimental studies on its single-molecule photoionization dissociation and pyrolysis product analysis worldwide.Therefore,in this thesis,empirical research on the photoionization dissociation and pyrolysis of MBO321 was carried out using synchrotron radiation vacuum ultraviolet photoionization mass spectrometry combined with a flow-tube reactor.The photodissociation products of MBO321 were obtained using Gaussian09 quantification software,and the photodissociation channels corresponding to all fragment ions were analyzed,and their dissociation reaction mechanisms were described in detail.The main research results are as follows:Firstly,this thesis investigates the photoionization dissociation reaction of MBO321 in the energy range of 8-15 e V.The ionization energy of the MBO321 molecule was determined to be 8.68 e V by continuous scanning photon energy.The fragment ions produced by photoionization dissociation of MBO321 were studied by combining synchrotron vacuum ultraviolet ionization mass spectrometry with photoionization efficiency curves:which were mainly divided into two types:direct dissociation to produce C₅H₉O⁺,C₄H₇O⁺,C₅H₉⁺,with indirect dissociation to produce C₅H₈⁺,C₅H₇⁺,CH₃CO⁺and C₃H₅⁺,and the appearance energies of each fragment ion were obtained as 9.52 e V,10.33 e V,9.61 e V,11.83 e V,11.68e V,10.96 e V,and 11.31 e V,respectively,and the branching ratios of fragment ions at different energies were calculated.In order to further get the detailed dissociation mechanism of the fragment ions,quantum chemical calculations of the photoionization dissociation of MBO321 were carried out in this thesis.Through the structural properties of MBO321 and fragment ions,the intermediates and transition states in the dissociation process of all fragment ions are analyzed and calculated.The possible dissociation channels of fragment ions are proposed by detailed study and calculation,the specific dissociation mechanism of fragment ions is analyzed,intramolecular migration of H and CH₃ dominates the dissociation process.The theoretical ionization energy and emergence potential obtained by calculation are in basic agreement with the experimental values.The photoionization mass spectra of MBO321 pyrolysis products were measured from 550 K to 1150 K by continuously changing the reaction temperature,while the photoionization efficiency curves of the pyrolysis products were measured by continuously scanning the photon energy at 1090K.The isomerization pyrolysis products of MBO321 were studied by combining photoionization mass spectra and photoionization efficiency spectra analysis.This thesis provides important reference information on the detailed photoionization-dissociation reaction mechanism of MBO321 through the above studies;it also provides important reference values on the combustion chemistry of MBO321.It provides an essential experimental and theoretical basis for the air pollution control and alternative fuel research of MBO321.