A comprehensive study on low-temperature oxidation chemistry of cyclohexane. I. Conformational analysis and theoretical study of first and second oxygen addition

Jiabiao Zou, Yuyang Li, Lili Ye, Hanfeng Jin

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11 Scopus citations

Abstract

To understand the low-temperature oxidation chemistry of cyclohexane, conformational analysis and theoretical study of the first and second oxygen addition are performed using quantum chemical calculations and kinetic calculations. Pressure- and temperature-dependent rate constants and branching ratios for major reaction channels are determined with RRKM/master-equation simulations over 298–2000 K and 0.01–1000 bar. The theoretical results indicate that the rapid inversion-topomerization processes facilitate fast equilibrium between axial and equatorial conformers. This can greatly counterbalance the influence of initial positions of side-chain groups in ROO, QOOH, cis-OOγQOOH and trans-OOγQOOH conformers. Conformational effects are found to be influential on the chain branching reaction sequences in second oxygen addition. The carbon ring prevents the conventional intramolecular H-transfer of cis-OOγQOOH conformers to yield ketohydroperoxides, as well as the inversion-topomerization from cis-OOγQOOH conformer to trans-OOγQOOH conformers. cis-OOγQOOH conformers mainly undergo alternative isomerization channel (cis-OOγQOOH→γP(OOH)2→alkenylhydroperoxides+OH→oxy radical+OH+OH), while trans-OOγQOOH conformers have both conventional isomerization channel (trans-OOγQOOH→ketohydroperoxides+OH→oxy radical+OH+OH) and alternative isomerization channel (trans-OOγQOOH→γP(OOH)2→alkenylhydroperoxides+OH→oxy radical+OH+OH). Kinetic calculation results also support the application of the thumb rule widely used in acyclic alkane oxidation that the rate constant of QOOH+O2 is roughly half of that of R+O2 in cyclic alkane oxidation, while it is indicated that estimating the rate constants of OOQOOH reactions from similar reactions of ROO may cause significant uncertainties.
Original languageEnglish (US)
Pages (from-to)111658
JournalCombustion and Flame
DOIs
StatePublished - Aug 21 2021

Bibliographical note

KAUST Repository Item: Exported on 2021-09-02
Acknowledgements: This work was supported by the National Natural Science Foundation of China (91841301, U1832171) and National Key R&D Program of China (2017YFE0123100). The quantum chemical calculation was performed on the High Performance Computing Cluster of Shanghai Jiao Tong University. The authors appreciate Prof. Feng Zhang, Prof. Lidong Zhang and Dr. Huiting Bian for their constructive suggestions.

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