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

Hanlin Fan; Jun Ma; Long Zhu; Bingzhi Liu; Fuyi Liu; Xiaobin Shan; Zhandong Wang; Liming Wang

doi:10.1021/acs.jpca.2c04382

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

J Phys Chem A. 2022 Nov 3;126(43):8021-8027. doi: 10.1021/acs.jpca.2c04382. Epub 2022 Oct 19.

Authors

Hanlin Fan¹, Jun Ma¹, Long Zhu², Bingzhi Liu², Fuyi Liu², Xiaobin Shan², Zhandong Wang², Liming Wang¹

Affiliations

¹ School of Chemistry & Chemical Engineering, South China University of Technology, Guangzhou 510640, China.
² National Synchrotron Radiation Laboratory, University of Sciences and Technology of China, Hefei, 230029, China.

PMID: 36259764
DOI: 10.1021/acs.jpca.2c04382

Abstract

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 ∼0.65% for KHP formation. Using synchrotron-generated vacuum-ultraviolet photoionization mass spectrometry measurements, 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.