STRUCTURE OF CARBON MONOXIDE

$^{*}$Formerly of the Theoretical Chemistry Department, Cambridge University, England. $^{1}$W. Moffitt, Proc. Roy. Soc. A, 196:510 (1949)Author Institution: University of Western OntarioA LCAO self-consistent-field procedure has been applied to the calculation of molecular orbitals and ionization energies of the ground state of the carbon monoxide molecule. The calculated molecular orbitals are in general agreement with Moffitt’s $predictions^{1}$ from semi-empirical evidence and considerations. The calculated ionization potentials are $-13,373$ e.v. for ($u\sigma$), $-15.969$ e.v. for ($\Pi_{u}$) and $-20.011$ e.v. for ($s\sigma$) compared with the experimental values $-14.009$ e.v., $-16.578$ e.v. and $-19.695$ e.v., respectively. The electronic structure of CO is discussed in terms of molecular orbitals and the electronic distribution in the CO molecule is compared with that of the CO group in the carbon dioxide molecule. A comparison of the electron density for CO and $CO_{2}$ as integrated over planes through points on the nuclear axis shows that whereas the distribution in carbon dioxide is symmetrical, that in carbon monoxide projects out slightly on the remote side from the bond. The low dipole moment and the formation of complexes of CO are explained as due to the presence of a lone pair of electrons on the remote side of the carbon atom. The CO molecule is shown to have a triple-bond structure (two $\Pi$ and one $\sigma$ bonding orbitals)