ENERGIES OF C2H5O AND C2H5O+ ISOMERS

The Gaussian-2 (G2) theoretical procedure, based on ab initio molecular orbital theory, is used to calculate the energies of C2H5O and C2H5O+ isomers. The ethoxy radical cation (CH3CH2O+) is found to have a 3A″ ground state while the singlet state is predicted to be unstable to rearrangement. The G2 adiabatic ionization potential of ethoxy radical is 10.32 eV in good agreement with a new ionization potential reported by Ruscic and Berkowitz of 10.29±0.08 eV from photoionization studies. The 2-hydroxyethyl radical (CH2CH2OH) has three isomers of nearly equal energy (within 1.6 kcal/mol). No stable 2-hydroxyethyl cation was located as it collapses to either O-protonated oxirane or 1-hydroxyethyl cation. The G2 appearance potential of CH3CHOH+ from ethanol of 10.79 eV is in excellent agreement with the recent photoionization value of 10.801±0.005 eV. The α(C-H), β(C-H), and O-H bond dissociation energies of ethanol are 94.9, 101.9, and 104.6 kcal/mol, respectively. The G2 result for the O-H bond energy is in good agreement with experiment while the results for the other two bond energies suggest that the experimental values for these quantities may be low. © 1995 American Institute of Physics.