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Gas-Phase Peroxyl Radical Recombination Reactions: A Computational Study of Formation and Decomposition of Tetroxides

[Image: see text] The recombination (“dimerization”) of peroxyl radicals (RO(2)•) is one of the pathways suggested in the literature for the formation of peroxides (ROOR′, often referred to as dimers or accretion products in the literature) in the atmosphere. It is generally accepted that these dime...

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Autores principales: Salo, Vili-Taneli, Valiev, Rashid, Lehtola, Susi, Kurtén, Theo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2022
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9251773/
https://www.ncbi.nlm.nih.gov/pubmed/35709531
http://dx.doi.org/10.1021/acs.jpca.2c01321
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author Salo, Vili-Taneli
Valiev, Rashid
Lehtola, Susi
Kurtén, Theo
author_facet Salo, Vili-Taneli
Valiev, Rashid
Lehtola, Susi
Kurtén, Theo
author_sort Salo, Vili-Taneli
collection PubMed
description [Image: see text] The recombination (“dimerization”) of peroxyl radicals (RO(2)•) is one of the pathways suggested in the literature for the formation of peroxides (ROOR′, often referred to as dimers or accretion products in the literature) in the atmosphere. It is generally accepted that these dimers play a major role in the first steps of the formation of submicron aerosol particles. However, the precise reaction pathways and energetics of RO(2)• + R′O(2)• reactions are still unknown. In this work, we have studied the formation of tetroxide intermediates (RO(4)R′): their formation from two peroxyl radicals and their decomposition to triplet molecular oxygen ((3)O(2)) and a triplet pair of alkoxyl radicals (RO•). We demonstrate this mechanism for several atmospherically relevant primary and secondary peroxyl radicals. The potential energy surface corresponds to an overall singlet state. The subsequent reaction channels of the alkoxyl radicals include, but are not limited to, their dimerization into ROOR′. Our work considers the multiconfigurational character of the tetroxides and the intermediate phases of the reaction, leading to reliable mechanistic insights for the formation and decomposition of the tetroxides. Despite substantial uncertainties in the computed energetics, our results demonstrate that the barrier heights along the reaction path are invariably small for these systems. This suggests that the reaction mechanism, previously validated at a multireference level only for methyl peroxyl radicals, is a plausible pathway for the formation of aerosol-relevant larger peroxides in the atmosphere.
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spelling pubmed-92517732022-07-05 Gas-Phase Peroxyl Radical Recombination Reactions: A Computational Study of Formation and Decomposition of Tetroxides Salo, Vili-Taneli Valiev, Rashid Lehtola, Susi Kurtén, Theo J Phys Chem A [Image: see text] The recombination (“dimerization”) of peroxyl radicals (RO(2)•) is one of the pathways suggested in the literature for the formation of peroxides (ROOR′, often referred to as dimers or accretion products in the literature) in the atmosphere. It is generally accepted that these dimers play a major role in the first steps of the formation of submicron aerosol particles. However, the precise reaction pathways and energetics of RO(2)• + R′O(2)• reactions are still unknown. In this work, we have studied the formation of tetroxide intermediates (RO(4)R′): their formation from two peroxyl radicals and their decomposition to triplet molecular oxygen ((3)O(2)) and a triplet pair of alkoxyl radicals (RO•). We demonstrate this mechanism for several atmospherically relevant primary and secondary peroxyl radicals. The potential energy surface corresponds to an overall singlet state. The subsequent reaction channels of the alkoxyl radicals include, but are not limited to, their dimerization into ROOR′. Our work considers the multiconfigurational character of the tetroxides and the intermediate phases of the reaction, leading to reliable mechanistic insights for the formation and decomposition of the tetroxides. Despite substantial uncertainties in the computed energetics, our results demonstrate that the barrier heights along the reaction path are invariably small for these systems. This suggests that the reaction mechanism, previously validated at a multireference level only for methyl peroxyl radicals, is a plausible pathway for the formation of aerosol-relevant larger peroxides in the atmosphere. American Chemical Society 2022-06-16 2022-06-30 /pmc/articles/PMC9251773/ /pubmed/35709531 http://dx.doi.org/10.1021/acs.jpca.2c01321 Text en © 2022 The Authors. Published by American Chemical Society https://creativecommons.org/licenses/by/4.0/Permits the broadest form of re-use including for commercial purposes, provided that author attribution and integrity are maintained (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Salo, Vili-Taneli
Valiev, Rashid
Lehtola, Susi
Kurtén, Theo
Gas-Phase Peroxyl Radical Recombination Reactions: A Computational Study of Formation and Decomposition of Tetroxides
title Gas-Phase Peroxyl Radical Recombination Reactions: A Computational Study of Formation and Decomposition of Tetroxides
title_full Gas-Phase Peroxyl Radical Recombination Reactions: A Computational Study of Formation and Decomposition of Tetroxides
title_fullStr Gas-Phase Peroxyl Radical Recombination Reactions: A Computational Study of Formation and Decomposition of Tetroxides
title_full_unstemmed Gas-Phase Peroxyl Radical Recombination Reactions: A Computational Study of Formation and Decomposition of Tetroxides
title_short Gas-Phase Peroxyl Radical Recombination Reactions: A Computational Study of Formation and Decomposition of Tetroxides
title_sort gas-phase peroxyl radical recombination reactions: a computational study of formation and decomposition of tetroxides
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9251773/
https://www.ncbi.nlm.nih.gov/pubmed/35709531
http://dx.doi.org/10.1021/acs.jpca.2c01321
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