Issue 16, 2018

Theoretical kinetic study of the formic acid catalyzed Criegee intermediate isomerization: multistructural anharmonicity and atmospheric implications

Abstract

We performed a theoretical study on the double hydrogen shift isomerization reaction of a six carbon atom Criegee intermediate (C6-CI), catalyzed by formic acid (HCOOH), to produce vinylhydroperoxide (VHP), C6-CI + HCOOH → VHP + HCOOH. This Criegee intermediate can serve as a surrogate for larger CIs derived from important volatile organic compounds like monoterpenes, whose reactivity is not well understood and which are difficult to handle computationally. The reactant HCOOH exerts a pronounced catalytic effect on the studied reaction by lowering the barrier height, but the kinetic enhancement is hindered by the multistructural anharmonicity. First, the rigid ring-structure adopted by the saddle point to facilitate simultaneous transfer of two atoms does not allow the formation of as many conformers as those formed by the reactant C6-CI. And second, the flexible carbon chain of C6-CI facilitates the formation of stabilizing intramolecular C–H⋯O hydrogen bonds; this stabilizing effect is less pronounced in the saddle point structure due to its tightness and steric effects. Thus, the contribution of the reactant C6-CI conformers to the multistructural partition function is larger than that of the saddle point conformers. The resulting low multistructural anharmonicity factor partially cancels out the catalytic effect of the carboxylic acid, yielding in a moderately large rate coefficient, k(298 K) = 4.9 × 10−13 cm3 molecule−1 s−1. We show that carboxylic acids may promote the conversion of stabilized Criegee intermediates into vinylhydroperoxides in the atmosphere, which generates OH radicals and leads to secondary organic aerosols, thereby affecting the oxidative capacity of the atmosphere and ultimately the climate.

Graphical abstract: Theoretical kinetic study of the formic acid catalyzed Criegee intermediate isomerization: multistructural anharmonicity and atmospheric implications

Supplementary files

Article information

Article type
Paper
Submitted
20 dec 2017
Accepted
29 jan 2018
First published
29 jan 2018

Phys. Chem. Chem. Phys., 2018,20, 10806-10814

Theoretical kinetic study of the formic acid catalyzed Criegee intermediate isomerization: multistructural anharmonicity and atmospheric implications

M. Monge-Palacios, M. P. Rissanen, Z. Wang and S. M. Sarathy, Phys. Chem. Chem. Phys., 2018, 20, 10806 DOI: 10.1039/C7CP08538A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements