The Reaction of Ozone with the C‒H Bond Revisited

ABSTRACT

This paper aimed at providing new insights into the mechanisms of ozone reactions with a selection of organic compounds, where C–H bonds were single available attack spots (1-propanol, tertiary-butanol, formate and formic acid). The involved method was based on the density functional theory (DFT). The calculations considered reactions occurring in a polar solvent, water (ɛ_r = 80), and a nonpolar one, cyclohexane (ɛ_r = 2.02). For all cases, the reaction was triggered by extraction of a hydrogen atom from the active C–H bond by ozone leading to a pair of radicals. Following this reaction, three situations occurred. Diffusion of the radicals from the solvent cage resulting in two free radicals meant H-abstraction. A fast electron transfer between the two radicals within the solvent cage resulting in the corresponding ions pair indicated pseudo hydride transfer. The recombination of the radicals within the solvent cage leading to an organic hydrotrioxide denoted pseudo insertion. In water, the systems might follow all pathways. In cyclohexane, the reaction might occur generally only via H-abstraction and pseudo insertion. An exception was the formate/O₃ system, where all pathways might occur.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ozone
• C‒H Bond
• DFT
• H-Abstraction
• Pseudo Hydride Transfer
• Pseudo Insertion

Acknowledgements

The authors thank Dr George A. Crisia of Aquatim S.A., Timişoara and Ing. Jens Richter of Westfaelische Hochschule Gelsenkirchen for their kind help.

Disclosure statement

No potential conflict of interest was reported by the author(s).