| Abstract: | Ab initio molecular orbital calculations have been carried out on all three isomers of difluoroethylene with geometry optimization. The calculations were done with a “double-zeta” basis set. After correction of the SCF energies for the effect of electron correlation, the 1,1-isomer is shown to be 8 kcal/mole lower in energy than the cis, which is 1 kcal/mole more stable than the trans. As the stabilization of the isomers increases, the distance between the fluorine atoms decreases: trans, 3.57 Å; cis, 2.77 Å; 1,1-isomer 2.20 Å. A simple explanation for these trends is based upon electrostatics and the small size and high electronegativity of the fluorine atom. As the fluorine atoms come closer together, the destabilization due to nuclear repulsions and electron repulsions is offset by the increased stabilizing electrons-nuclei attractions. |
