The calculations of charge distributions, bond orders and conformations for a number of oxygen- and fluorine-containing molecules by CNDO-BW and EHT me

Abstract

The electronic structure for a number of highly fluorinated ethanes, ketones and aldehydes has been calculated using the CNDO-BW method. Bond orders for these molecules were obtained by the Wiberg method, by the transformation to the basis of hybrid Orbitals and from the Mulliken's population analysis. The method cannot describe internal rotation barriers. A sufficiently reliable bond order-bond length correlation for both C-C and C-O bonds appears impossible to find. The most stable conformations for the given molecules seem to be defined by the minimum of coulomb interaction energy of atomic charges. Valence angles can be calculated with precision. The charge distributions obtained correspond to the available data on the chemistry and IR spectroscopy of these molecules. The EHT method is shown to be incorrect when both the most stable conformations and charge distributions are considered.