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

Title of the article: About formation and structure of transition state during "chair" to "boat" transition of cyclohexanone

Year: 2022, Issue: 1, Pages: 56-63

Branch of knowledge: 2.6.10. Organic matter technology

Index UDK: 544.43:547-316

DOI: 10.26730/1999-4125-2022-1-56-63

Abstract: By the density functional theory (DFT) method of with hybrid functional B3LYP in the basis 6-31G for the cyclohexanone molecule, a scan was carried out on the coordinate of the conformational transition "chair"-"boat". It has been shown that such a "chair"-" boat" transition energetically more preferably proceeds through a change in the geometric parameters of the "carbonyl" fragment of the ketone molecule. By the QST2 and QST3 methods (Quadratic Synchronous Transit Approach) the transition state of the conformational transition "chair"-"boat" of the cyclohexanone molecule is localized. There was confirmed that all structures are stationary points on the surface of potential energy. Geometric characteristics of the transition state of the conformational transition "chair"-"boat" of the cyclohexanone molecule are determined: bond lengths and valence angles. The geometry of the transition state of the conformational transition "chair"-"boat" was close to the geometry of the conformation "sofa" of the cyclohexanone molecule. The total energies of the transition state of the conformational transition "chair"-"boat" and the conformations "chair" and "boat" of cyclohexanone are calculated. The activation energies of the direct and reverse reactions of the conformational transition "chair" – "boat" are calculated. It is shown that the transition "chair"-"boat" is an endothermic reaction, and the return transition "boat"-"chair" is exothermic. The conformation energy of the cyclohexanone "boat" is 16.3 kJ/mol higher than the conformation energy of the "chair".

Key words: cyclohexanone conformations reactivity "chair" "boat" quantum chemistry methods transition state activation energy

Receiving date: 30.12.2021

Approval date: 30.01.2022

Publication date: 25.02.2022

CITE DOWNLOAD