Unusual Diradical Intermediates in Ozonolysis of Alkenes: A Combined Theoretical and Synchrotron Radiation Photoionization Mass Spectrometric Study on Ozonolysis of Alkyl Vinyl Ethers

作者：Fan, Hanlin; Ma, Jun; Zhu, Long; Liu, Bingzhi; Liu, Fuyi; Shan, Xiaobin; Wang, Zhandong^*; Wang, Liming^*

来源：The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment & general theory, 2022, 126(43): 8021-8027.

DOI：10.1021/acs.jpca.2c043828021J

• SIMPLEST CRIEGEE INTERMEDIATE
• GAS-PHASE OZONOLYSIS
• MOLECULAR-STRUCTURE
• PRIMARY OZONIDE
• OH
• MECHANISM
• OXIDATION
• KINETICS
• CONFORMATION
• CONVERGENCE

Calculations and experiments were conducted on ozonolysis of ethyl vinyl ether (EVE) and butyl vinyl ether to identify an unconventional diradical intermediate generated from the O-O bond cleavage of primary ozonide. The diradical can undergo a H atom shifting process that yields keto-hydroperoxide (KHP), the characteristic product that identifies the existence of a diradical intermediate. RRKM-ME calculation, based on the PES at the CCSD(T)/VTZ//M06-2X/6-311+ +G(2df,2p) level, disclosed branching ratios of similar to 0.65% for KHP formation. Using synchrotron-generated vacuum-ultraviolet photoionization mass spectrometry measure-ments, the formation of KHPs (C4H8O4) in ozonolysis of EVE was confirmed by ion signals of C4H8O4+ (ionization of KHP) and C4H7O2+ (ion fragment from the loss of HO2 from KHP) by comparing their photoionization efficiency spectra with the calculated adiabatic ionization energies and appearance energies.