Investigation of the stereoelectronic properties in 1,2-difluorocyclopropane and 1,2-difluorocyclohexane: Evaluation of the gauche effect

The gauche effect, the phenomenon of approximating (dihedral angle about 60°) electronegative atoms or groups in a 1,2-disubstituted ethane fragment, is theoretically evaluated in this report, taking 1,2-difluorocyclopropane and 1,2-difluorocyclohexane (cis and trans) as models. NBO analysis was used in order to give insight into the nature of the gauche effect in the studied compounds, i.e. its origin has been evaluated as due to hyperconjugation or to bent bonds.