Theoretical study of the C–H bond dissociation energy of acetylene

A systematic study of the energies of acetylene and ethynyl radical and cation using high levels of ab initio molecular orbital theory, including correlation effects beyond fourth order perturbation theory, is presented. The bond dissociation energy of acetylene D0(HCC–H), is calculated to be 5.79 eV with an expected accuracy of ±0.1 eV. The 3Π ground state of C2H+ is calculated to be 0.36 eV more stable than the 3Σ− state. The ionization potential of ethynyl radical (C2H) is calculated to be 11.65 eV.