Issue 14, 2020

Unimolecular decomposition rates of a methyl-substituted Criegee intermediate syn-CH3CHOO

Abstract

Criegee intermediates play important roles in atmospheric chemistry. Methyl Criegee intermediate, CH3CHOO, has two conformers, syn- and anti-conformers. Syn-CH3CHOO would undergo fast unimolecular decomposition to form OH radical via 1,4 H-atom transfer. In this work, unimolecular decomposition of syn-CH3CHOO was probed in real time with UV absorption spectroscopy at 278–318 K and 100–700 torr. We used water vapor as the scavenger of anti-CH3CHOO to distinguish the absorption signals of the two conformers. After removing the contributions from reactions with radical byproducts, reaction with water vapor and wall loss, we obtained the unimolecular reaction rate coefficient of syn-CH3CHOO (at 300 torr), which increases from (67 ± 15) s−1 at 278 K, (146 ± 31) s−1 at 298 K, to (288 ± 81) s−1 at 318 K with an Arrhenius activation energy of ca. 6.4 kcal mol−1 and a weak pressure dependence for 100–700 torr. Compared to previous studies, this work provides temperature dependent unimolecular rates of syn-CH3CHOO at higher pressures, which are more relevant to atmospheric conditions.

Graphical abstract: Unimolecular decomposition rates of a methyl-substituted Criegee intermediate syn-CH3CHOO

Supplementary files

Article information

Article type
Paper
Submitted
09 Jan 2020
Accepted
18 Feb 2020
First published
28 Feb 2020
This article is Open Access
Creative Commons BY license

RSC Adv., 2020,10, 8518-8524

Unimolecular decomposition rates of a methyl-substituted Criegee intermediate syn-CH3CHOO

Y. Li, M. Kuo and J. J. Lin, RSC Adv., 2020, 10, 8518 DOI: 10.1039/D0RA01406K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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