Authors: S.V. Puchkov, Yu.V. Nepomnyashchikh

Title of the article: "Chair" - "boat" conformational transition of cyclohexanol during cyclohexane oxidation

Year: 2026, Issue: 1, Pages: 56-64

Branch of knowledge: 2.6.10. Organic matter technology

Index UDK: 544.43:547-31

DOI: 10.26730/1999-4125-2026-1-56-64

Abstract: The industrial process of liquid-phase cyclohexane oxidation is the most important step in large-scale production of monomers for the polyamide fibers manufacturing. The low selectivity of this process leads to the maintenance of a low conversion rate, which leads to an increase in the cost of separating unreacted cyclohexane and recycling it. An increase in the volume of raw materials to maintain productivity with a low conversion rate leads to an increase in the size of the equipment and, as a result, capital expenditures, depreciation and cost of finished products. The selectivity of the cyclohexane oxidation process depends on many factors, including the conversion rates of the reactant and the desired reaction products cyclohexanol and cyclohexanone in sequential and parallel reactions. The link between the selectivity of the cyclohexanol oxidation process and the reactions of the "chair" - "boat" conformational transitions of cyclohexanol, as well as the effect of the composition of conformers on the process parameters, have not been studied. The purpose of the work was to study the kinetic parameters of the "chair" - "boat" conformational transition of cyclohexanol and the effect of the composition of alcohol conformers on the selectivity of the cyclohexane oxidation process. Using quantum chemical methods, the activation energies, enthalpy and entropy of the "chair" - "boat" conformational transition of cyclohexanol were calculated. Gibbs energies and temperature dependencies of equilibrium constants of conformational transitions of cyclohexanol are determined. It has been shown that the composition of cyclohexanol conformers affects the selectivity of the cyclohexane oxidation process. An increase in the composition more reactive conformation leads to a decrease in selectivity. It was found that as the temperature increases, the equilibrium of conformational transitions shifts towards the formation of more reactive conformers, the conversion rate of which is higher, which leads to a decrease in the selectivity of the process, so it which concludes need to conduct the cyclohexane oxidation process at the lowest possible temperature.

Key words: cyclohexane oxidation cyclohexanol quantum chemical calculation conformation "chair" "boat"

Receiving date: 03.07.2025

Approval date: 15.01.2026

Publication date: 19.03.2026

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