Thermodynamic Properties of the Acetyl Radical and Bond Dissociation Energies in Aliphatic Carbonyl Compounds

Photoionization mass spectrometry was used to study the thermodynamic properties of the acetyl radical and to determine bond energies in acetone and biacetyl. From measured appearance potentials of CH3CO+ and by the use of thermodynamic cycles, the following bond energies were determined: D0(CH3–CO)=0.49±0.03 eV, D0(CH3CO–CH3)=3.34±0.06 eV and D0(CH3CO–COCH3)=2.84±0.06 eV. D0(CH3CO–H) is calculated to be 3.69±0.06 eV. ΔHf°(CH3CO) is calculated to be —0.28±0.06 eV.