Theoretical study of the kinetics of F-atom abstraction reactions from F₂, CF₂(OF)₂, CF₃OF and SF₅OF by CO

Abstract

The kinetics of the fluorine atom abstraction reactions RF+CO→R+FCO (with R=F, CF₂(OF)O, CF₃O, and SF₅O) has been theoretically studied using the density functional theory and ab initio composite models. The derived average activation energies for the reactions of CO with F₂ and with CF₂(OF)₂ of 15.4 kcal mol⁻¹, at 290–320 K, and 23.1 kcal mol⁻¹, at 386–420 K, are in good agreement with the experimental ones. For the F-atom abstraction from the CF₃OF and SF₅OF molecules, values of 22.7 and 22.5 kcal mol⁻¹ were calculated. Over the 290–320 and 386–420 K temperature ranges, preexponential factors of 1.1 × 10⁻¹² and 4.4 × 10⁻¹² cm³ molecule⁻¹ s⁻¹ were respectively determined for the reactions of CO with F₂ and CF₂(OF)₂ which are 60% larger than the experimental. Values of 2.3 × 10⁻¹² and 1.2 × 10⁻¹² cm³ molecule⁻¹ s⁻¹ were obtained for the reactions corresponding to the SF₅OF and CF₃OF molecules at 353–383 and 383–423 K, respectively. Unexpectedly, the ωB97X-D, M06-2X and BMK functionals lead to energy barriers much higher than those predicted by other quantum-chemical models.

GRAPHICAL ABSTRACT

KEYWORDS:

• Abstraction reactions
• F₂
• CF₂(OF)₂
• CF₃OF
• SF₅OF

Acknowledgements

The authors wish to thank Professor Jürgen Troe for a lifelong encouragement and generous support.

Disclosure statement

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

Additional information

Funding

This research project was supported by the Universidad Nacional de La Plata under Grant X842; the Agencia Nacional de Promoción Científica y Tecnológica under Grant PICT-2018-03738.