Chemical Physics Letters vol:287 issue:1-2 pages:109-118
The reaction of the ethynyl radical with molecular oxygen has been examined using density functional theory. Two major reaction routes are open to the chemically activated HCCOO adduct 1: dissociation to HCCO + O 16 and formation of the thermodynamically most stable products HCO + CO 12. HCCOO 1 --> dioxirenyl 2 --> oxyrenyloxy 3 --> oxo-ketene 5 --> HCO + CO 12 --> H + 2CO 15. The CCSD(T)/6-311 + + G(d,p)//B3LYP/6-311 + + G(d,p) energies of the respective rate controlling transition states, 1/16 and 1/2, indicate that the route leading to H + CO + CO should dominate. Several other [C-2,H,O-2] isomers and other, minor pathways have also been characterised. The present study reveals this reaction to be a capture-limited association-elimination reaction with a high and pressure-independent rate coefficient. (C) 1998 Elsevier Science B.V. All rights reserved.