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J Am Chem Soc

Title:		Online Quantification of Criegee Intermediates of alpha-Pinene Ozonolysis by Stabilization with Spin Traps and Proton-Transfer Reaction Mass Spectrometry Detection
Author(s):		Giorio C; Campbell SJ; Bruschi M; Tampieri F; Barbon A; Toffoletti A; Tapparo A; Paijens C; Wedlake AJ; Grice P; Howe DJ; Kalberer M;
Address:		"Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom. Dipartimento di Scienze dell'Ambiente e del Territorio e di Scienze della Terra, Universita degli Studi di Milano Bicocca , Piazza della Scienza 1, Milano 20126, Italy. Dipartimento di Scienze Chimiche, Universita degli Studi di Padova , via Marzolo 1, Padova 35131, Italy"
Journal Title:		J Am Chem Soc
Year:		2017
Volume:		20170307
Issue:		11
Page Number:		3999 - 4008
DOI:		10.1021/jacs.6b10981
ISSN/ISBN:		1520-5126 (Electronic) 0002-7863 (Linking)
Abstract:		"Biogenic alkenes, which are among the most abundant volatile organic compounds in the atmosphere, are readily oxidized by ozone. Characterizing the reactivity and kinetics of the first-generation products of these reactions, carbonyl oxides (often named Criegee intermediates), is essential in defining the oxidation pathways of organic compounds in the atmosphere but is highly challenging due to the short lifetime of these zwitterions. Here, we report the development of a novel online method to quantify atmospherically relevant Criegee intermediates (CIs) in the gas phase by stabilization with spin traps and analysis with proton-transfer reaction mass spectrometry. Ozonolysis of alpha-pinene has been chosen as a proof-of-principle model system. To determine unambiguously the structure of the spin trap adducts with alpha-pinene CIs, the reaction was tested in solution, and reaction products were characterized with high-resolution mass spectrometry, electron paramagnetic resonance, and nuclear magnetic resonance spectroscopy. DFT calculations show that addition of the Criegee intermediate to the DMPO spin trap, leading to the formation of a six-membered ring adduct, occurs through a very favorable pathway and that the product is significantly more stable than the reactants, supporting the experimental characterization. A flow tube set up has been used to generate spin trap adducts with alpha-pinene CIs in the gas phase. We demonstrate that spin trap adducts with alpha-pinene CIs also form in the gas phase and that they are stable enough to be detected with online mass spectrometry. This new technique offers for the first time a method to characterize highly reactive and atmospherically relevant radical intermediates in situ"
Keywords:		Alkenes/*analysis Atmosphere/chemistry Kinetics Mass Spectrometry *Online Systems Oxides/*analysis Ozone/*chemistry *Protons Quantum Theory;
Notes:		"MedlineGiorio, Chiara Campbell, Steven J Bruschi, Maurizio Tampieri, Francesco Barbon, Antonio Toffoletti, Antonio Tapparo, Andrea Paijens, Claudia Wedlake, Andrew J Grice, Peter Howe, Duncan J Kalberer, Markus eng Research Support, Non-U.S. Gov't 2017/02/17 J Am Chem Soc. 2017 Mar 22; 139(11):3999-4008. doi: 10.1021/jacs.6b10981. Epub 2017 Mar 7"