ABINITIO MOLECULAR-ORBITAL STUDY OF C3H8O+ IONS

Several parent ion structures as well as dissociated product structures relevant to the dissociation of 1-propanol ions have been investigated by ab initio molecular orbital calculations. The species studied include the 1-propanol molecular ion, CH3CH2CH2OH+, the distonic ion, CH2CH2CH2OH2+, the ion-dipole complex, c-C3H6+-H2O, and a hydronium ion-allyl radical complex. In addition, the structures and energies of the transition states connecting these isomers and their dissociation products have been determined. The calculations were carried out with the GAUSSIAN 90 program using thc 6-31G* and 6-31G** basis sets, the latter with inclusion of electron correlation by using Moller-Plesset perturbation theory truncated at second order. All bond lengths and angles were optimized and vibrational frequencies calculated. These calculations showed that the H loss channel and the rearrangement to the distonic ion are associated with substantial barriers. On the other hand, the distonic ion is separated from the ion-dipole complex by a relatively low barrier. The major finding is that the lower energy isomer of the propanol ion, in which the electron is removed from the sigma-bond between the alpha and beta-carbons, lies 0.6 eV below the reported propanol ion heat of formation. The geometries, charge distributions, and vibrational frequencies are reported in this publication. An accompanying paper discusses the dissociation dynamics of propanol ions.