Wang Huanhuan, Huang Mingqiang, Chen Hao, Shan Xiaobin, Wang Zhenya, Liu Fuyi, Sheng Liusi
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, China.
Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, College of Chemistry and Chemical Engineering and Environment, Minnan Normal University, Zhangzhou, China.
J Mass Spectrom. 2023 Aug;58(8):e4967. doi: 10.1002/jms.4967.
This study employed a vacuum ultraviolet synchrotron radiation source and reflectron time-of-flight mass spectrometry (TOF-MS) to investigate the photoionization and dissociation of styrene. By analyzing the photoionization mass spectrum and efficiency curve alongside G3B3 theoretical calculations, we determined the ionization energy of the molecular ion, appearance energy of fragment ions, and relevant dissociation pathways. The major ion peaks observed in the photoionization mass spectra of styrene correspond to C H , C H and C H . The ionization energy of styrene is measured as 8.46 ± 0.03 eV, whereas the appearance energies of C H and C H are found to be 12.42 ± 0.03 and 12.22 ± 0.03 eV, respectively, in agreement with theoretical values. The main channel for the photodissociation of styrene molecular ions is the formation of benzene ions, whereas the dissociation channel that loses hydrogen atoms is the secondary channel. Based on the experimental results and empirical formulas, the required dissociation energies (E ) of C H , C H and C H are calculated to be (3.96 ± 0.06), (4.00 ± 0.06) and (3.76 ± 0.06) eV, respectively. Combined with related thermochemical parameters, the standard enthalpies of formations of C H , C H , C H and C H are determined to be 964.2, 1346.3, 1350.2 and 1327.0 kJ/mol, respectively. Based on the theoretical study, the kinetic factors controlling the styrene dissociation reaction process are determined by using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. This provides a reference for further research on the atmospheric photooxidation reaction mechanism of styrene in atmospheric and interstellar environments.
