ABINITIO THEORETICAL-STUDY OF THE HC2+CO REACTION AND THE HC2CO RADICAL

The ethynyl radical, carbon monoxide, and their product (HC2CO) have been studied at the self-consistent field (SCF), configuration interaction, and coupled cluster correlation level including all single and double excitations (CISD and CCSD, respectively). The basis sets employed were of double zeta-plus polarization (DZP) and triple zeta-plus double polarization (TZ2P) quality. The geometries were optimized at both the SCF and CISD levels of theory. The energetics of the reaction were also studied by employing the open-shell coupled cluster method. A nonlinear HC2CO product was found to be a minimum while the linear HC2CO structure proved to be a stationary point with two imaginary frequencies. Our best theoretical prediction after correction for basis set superposition error and zero-point vibrational energy yields for HC2CO a binding energy of 20.0 kcal/mol with a very small (0.8 kcal/mol) activation barrier. Vibrational frequencies are also presented.