The force constants in the isoelectronic series CF3SO2X (X=F, OH, NH2, CH3): a study based on DFT calculations and experimental data

Density functional theory calculations at the B3LYP/6-31G(d,p) level of theory were performed on the members of the isoelectronic series CF₃SO₂X (X=F, OH, NH₂, CH₃), in order to obtain the optimized geometric parameters and conformations for the four molecules, as well as the wavenumbers corresponding to the normal modes of vibration and the associated force constants. The original force field was transformed to local symmetry coordinates and scaled to reproduce the experimental wavenumbers. The trends observed in geometrical parameters and force constants along the isoelectronic series could be explained making use of the calculated atomic charges.