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Computational Investigation of Substituent Effects on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions
[Image: see text] Organic peroxy radicals (RO(2)) are key intermediates in atmospheric chemistry and can undergo a large variety of both uni- and bimolecular reactions. One of the least understood reaction classes of RO(2) are their self- and cross-reactions: RO(2) + R′O(2). In our previous work, we...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Chemical Society
2023
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9969516/ https://www.ncbi.nlm.nih.gov/pubmed/36753050 http://dx.doi.org/10.1021/acs.jpca.2c08927 |
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author | Hasan, Galib Salo, Vili-Taneli Golin Almeida, Thomas Valiev, Rashid R. Kurtén, Theo |
author_facet | Hasan, Galib Salo, Vili-Taneli Golin Almeida, Thomas Valiev, Rashid R. Kurtén, Theo |
author_sort | Hasan, Galib |
collection | PubMed |
description | [Image: see text] Organic peroxy radicals (RO(2)) are key intermediates in atmospheric chemistry and can undergo a large variety of both uni- and bimolecular reactions. One of the least understood reaction classes of RO(2) are their self- and cross-reactions: RO(2) + R′O(2). In our previous work, we have investigated how RO(2) + R′O(2) reactions can lead to the formation of ROOR′ accretion products through intersystem crossings and subsequent recombination of a triplet intermediate complex (3)(RO···OR′). Accretion products can potentially have very low saturation vapor pressures, and may therefore participate in the formation of aerosol particles. In this work, we investigate the competing H-shift channel, which leads to the formation of more volatile carbonyl and alcohol products. This is one of the main, and sometimes the dominant, RO(2) + R′O(2) reaction channels for small RO(2). We investigate how substituents (R and R′ groups) affect the H-shift barriers and rates for a set of (3)(RO···OR′) complexes. The variation in barrier heights and rates is found to be surprisingly small, and most computed H-shift rates are fast: around 10(8)–10(9) s(–1). We find that the barrier height is affected by three competing factors: (1) the weakening of the breaking C–H bond due to interactions with adjacent functional groups; (2) the overall binding energy of the (3)(RO···OR′), which tends to increase the barrier height; and (3) the thermodynamic stability of the reaction products. We also calculated intersystem crossing rate coefficients (ISC) for the same systems and found that most of them were of the same order of magnitude as the H-shift rates. This suggests that both studied channels are competitive for small and medium-sized RO(2). However, for complex enough R or R′ groups, the binding energy effect may render the H-shift channel uncompetitive with intersystem crossings (and thus ROOR′ formation), as the rate of the latter, while variable, seems to be largely independent of system size. This may help explain the experimental observation that accretion product formation becomes highly effective for large and multifunctional RO(2). |
format | Online Article Text |
id | pubmed-9969516 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2023 |
publisher | American Chemical Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-99695162023-02-28 Computational Investigation of Substituent Effects on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions Hasan, Galib Salo, Vili-Taneli Golin Almeida, Thomas Valiev, Rashid R. Kurtén, Theo J Phys Chem A [Image: see text] Organic peroxy radicals (RO(2)) are key intermediates in atmospheric chemistry and can undergo a large variety of both uni- and bimolecular reactions. One of the least understood reaction classes of RO(2) are their self- and cross-reactions: RO(2) + R′O(2). In our previous work, we have investigated how RO(2) + R′O(2) reactions can lead to the formation of ROOR′ accretion products through intersystem crossings and subsequent recombination of a triplet intermediate complex (3)(RO···OR′). Accretion products can potentially have very low saturation vapor pressures, and may therefore participate in the formation of aerosol particles. In this work, we investigate the competing H-shift channel, which leads to the formation of more volatile carbonyl and alcohol products. This is one of the main, and sometimes the dominant, RO(2) + R′O(2) reaction channels for small RO(2). We investigate how substituents (R and R′ groups) affect the H-shift barriers and rates for a set of (3)(RO···OR′) complexes. The variation in barrier heights and rates is found to be surprisingly small, and most computed H-shift rates are fast: around 10(8)–10(9) s(–1). We find that the barrier height is affected by three competing factors: (1) the weakening of the breaking C–H bond due to interactions with adjacent functional groups; (2) the overall binding energy of the (3)(RO···OR′), which tends to increase the barrier height; and (3) the thermodynamic stability of the reaction products. We also calculated intersystem crossing rate coefficients (ISC) for the same systems and found that most of them were of the same order of magnitude as the H-shift rates. This suggests that both studied channels are competitive for small and medium-sized RO(2). However, for complex enough R or R′ groups, the binding energy effect may render the H-shift channel uncompetitive with intersystem crossings (and thus ROOR′ formation), as the rate of the latter, while variable, seems to be largely independent of system size. This may help explain the experimental observation that accretion product formation becomes highly effective for large and multifunctional RO(2). American Chemical Society 2023-02-08 /pmc/articles/PMC9969516/ /pubmed/36753050 http://dx.doi.org/10.1021/acs.jpca.2c08927 Text en © 2023 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 | Hasan, Galib Salo, Vili-Taneli Golin Almeida, Thomas Valiev, Rashid R. Kurtén, Theo Computational Investigation of Substituent Effects on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions |
title | Computational Investigation of Substituent Effects
on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions |
title_full | Computational Investigation of Substituent Effects
on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions |
title_fullStr | Computational Investigation of Substituent Effects
on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions |
title_full_unstemmed | Computational Investigation of Substituent Effects
on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions |
title_short | Computational Investigation of Substituent Effects
on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions |
title_sort | computational investigation of substituent effects
on the alcohol + carbonyl channel of peroxy radical self- and cross-reactions |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9969516/ https://www.ncbi.nlm.nih.gov/pubmed/36753050 http://dx.doi.org/10.1021/acs.jpca.2c08927 |
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