“Chair”–“Boat” Conformational Transition of Cyclohexanone during the Oxidation of Cyclohexane

The B3LYP/6-311g++(d,p), G3, and CBS-QB3 methods (DFT) have been used to calculate the free energy and equilibrium constants of the “chair”–“boat” conformational transition of cyclohexanone in the temperature range 298.15–428.15 K. The equilibrium composition of the chair and boat conformers of cyclohexanone has been calculated. It has been shown that with an increase in the proportion of the boat conformation, the selectivity of the process of cyclohexane oxidation to cyclohexanone decreases. The transition states of addition reactions of cyclohexyl hydroperoxide at the carbonyl group of cyclohexanone for chair and boat conformations have been found by the QST2 method. The energy profiles of these reactions have been calculated. It has been established that the addition of hydroperoxide to the carbonyl group of the boat conformation of the ketone is accompanied by a transition to the chair conformation.