Spectroscopy of CH3CO(-) and CH3CO

Article abstract of DOI:10.1021/ja00202a001

We have measured the photoelectron spectra of CH3CO(-) and CH2DCO(-) and find the following electron affinities: EA(CH3CO) = 0.423 +/- 0.037 eV and EA(CH2DCO) = 0.418 +/- 0.038 eV.The spectra show excitation the C-C-O bending vibration of the radical, and we have measured the following bending frequencies: ν₁₁(CH3CO) = 490 +/- 30 cm^-1, ν₁₁(CH2DCO) = 500 +/- 50 cm^-1, and ν₁₁(CH3CO(-)) = 570 +/- 180 cm^-1.From a Franck-Condon analysis of the vibronic peak intensities we have estimated these C-C-O bond angles for the acetyl anion and radical:α(CCO) = 110 +/- 5⁰ and α(CCO) = 133 +/- 5⁰.These angles are consistent with ab initio Hartree-Fock geometry optimizations of both the ion and radical (in a triple-ζ plus polarization basis set).Finally, the electron affinities we have measured can be used to determine the following thermodynamic parameters: ΔH_f⁰₂₉₈(CH3CO) = -5.4 +/- 2.1 kcal/mol, ΔH_f⁰₂₉₈(CH3CO(-)) = -14.9 +/- 2.3 kcal/mol, DH₂₉₈(CH3-CO) = 10.6 +/- 2.2 kcal/mol, and DH₂₉₈((-)CH3-CO) = 17.6 +/- 2.3 kcal/mol.