New Approach to the Detection of Short-Lived Radical Intermediates

Peter J.H. Williams, Graham A. Boustead, Dwayne E. Heard, Paul W. Seakins, Andrew R. Rickard*, Victor Chechik

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We report a new general method for trapping short-lived radicals, based on a homolytic substitution reaction SH2′. This departure from conventional radical trapping by addition or radical-radical cross-coupling results in high sensitivity, detailed structural information, and general applicability of the new approach. The radical traps in this method are terminal alkenes possessing a nitroxide leaving group (e.g., allyl-TEMPO derivatives). The trapping process thus yields stable products which can be stored and subsequently analyzed by mass spectrometry (MS) supported by well-established techniques such as isotope exchange, tandem MS, and high-performance liquid chromatography-MS. The new method was applied to a range of model radical reactions in both liquid and gas phases including a photoredox-catalyzed thiol-ene reaction and alkene ozonolysis. An unprecedented range of radical intermediates was observed in complex reaction mixtures, offering new mechanistic insights. Gas-phase radicals can be detected at concentrations relevant to atmospheric chemistry.

Original languageEnglish
Pages (from-to)15969−15976
Number of pages8
JournalJournal of the American Chemical Society
Issue number35
Early online date24 Aug 2022
Publication statusPublished - 7 Sept 2022

Bibliographical note

© 2022 The Authors. Published by American Chemical Society.

Funding Information:
This study was supported by the Engineering and Physical Sciences Research Council Doctoral Training Partnership award EP/N509802/1. We thank J. F. Hamilton and T. J. Dillon for helpful discussions and E. Bergstrom (York Centre of Excellence for Mass Spectrometry) for advice and assistance with running MS instruments. K. A. Read is thanked for help with ozone instruments and calibration at York.

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