The conformation of alkyl cyclohexanones and terpenic ketones. Interpretation for the 'alkylketone effect' based on the CH/π(CO) hydrogen bond

Ab initio MO calculations were carried out to investigate the Gibbs free energy of the conformational isomers of cyclohexanone derivatives. The genesis of the stabilization of the axial conformers in 2- and 3-alkyl cyclohexanones has been attributed to the attractive, five-membered CH/π(CO) hydrogen bond.