Rate coefficients of H-atom abstraction from ethers and isomerization of alkoxyalkylperoxy radicals

Abstract

Group rate expressions for the hydrogen(H)-atom abstraction reactions from ethers by hydrogen atoms and hydroxyl(OH) radicals and the intramolecular hydrogen-transfer isomerization reactions of alkoxyalkylperoxy radicals, which result from the H-abstraction from ethers followed by the addition of O₂, have been evaluated based on the quantum chemical calculations and experimental data. With the relative method proposed in the present study, it was shown that the rate coefficients of the reactions, for which only poor experimental information is available, can be reliably evaluated by calculating and extracting the difference from the well-established reactions of alkane hydrocarbons. The major features on the H-abstraction reactions from O-adjacent sites of ethers compared to those from alkanes were the suppression of the activation energy due to the decrease of the C–H bond dissociation energy and non-next neighbor substituent effect from the alkyl group on the counter side of –O–. For the hydrogen transfer isomerization reactions, similar suppression of the activation energy as well as the change in the ring strain energy was found as a major feature.