Issue 42, 2017

The reaction of Criegee intermediates with acids and enols

Abstract

The reaction of CH2OO, the smallest carbonyl oxide (Criegee intermediate, CI), with several acids was investigated using the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ quantum chemical method, as well as microvariational transition state theory and RRKM master equation theoretical kinetic methodologies. For oxoacids HNO3 and HCOOH, a 1,4-insertion mechanism allows for barrierless reactions with high rate coefficients, in agreement with literature experimental data. This mechanism relies on the presence of a double bond in the α-position to the acidic OH group. We predict that reactions of CI with enols will likewise have high rate coefficients, proceeding through a similar mechanism. The hydracid HCl was found to react through a less favorable 1,2-insertion reaction, leading to lower rate coefficients, again in good agreement with the literature. We conclude that the reaction mechanism is the main indicator for the reaction rate for CH2OO + acid reactions, with acidity only of secondary influence. At room temperature and 1 atm the main product for all reactions was found to be the thermalized hydroperoxide initial adduct, with minor yields of fragmentation products. One of the product channels characterized is a novel reaction path involving intramolecular H-abstraction after a roaming reaction in the OH + product radical complex formed by the dissociation of the hydroperoxide adduct; this channel is the lowest fragmentation route for some of the reactions studied.

Graphical abstract: The reaction of Criegee intermediates with acids and enols

Supplementary files

Article information

Article type
Paper
Submitted
28 Jul 2017
Accepted
04 Oct 2017
First published
05 Oct 2017

Phys. Chem. Chem. Phys., 2017,19, 28630-28640

The reaction of Criegee intermediates with acids and enols

L. Vereecken, Phys. Chem. Chem. Phys., 2017, 19, 28630 DOI: 10.1039/C7CP05132H

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