Temporary Anion States of Dichloroalkanes and Selected Polychloroalkanes

Abstract

The electron attachment energies associated with the short-lived occupation of the C−Cl σ* orbitals of dichloroalkanes and selected polychloroalkanes are measured in the gas phase using electron transmission spectroscopy and compared with those observed previously in monochloroalkanes. In the dichloroalkanes, evidence for two well-resolved anion states is found only in the compounds with both chlorines on the same carbon atom. The effects of methyl substitution on chlorine-bearing carbon atoms are examined in detail and are observed to stabilize temporary anion states lying above ∼1.5 eV but to destabilize those lying below. The spread in energy of the anion states, attributable to their finite lifetimes, is examined as a function of the vertical attachment energies (VAEs) of the anions and found to vary as VAE1.5, consistent with the relationship expected on theoretical grounds for the monochloroalkanes. Calculated energies of the lowest unoccupied molecular orbitals (LUMOs) are also presented and compared with the measured VAEs.