Ketenyl radical (HCCO) is an important hydrocarbon combustion intermediate. The mechanisms and kinetics for the reaction of HCCO (X 2 A″) with H( 2 S) occurring on both singlet and triplet surfaces have been studied by a combination of ab initio calculations and rate constant predictions at the CCSD(T)/6-311++G(3df,2p)//CCSD/6-311++G(d,p) level of theory. The kinetics and product branching ratios have been investigated in the temperature range of 297–3000 K by variational transition state and Rice–Ramsperger–Kassel–Marcus (RRKM) theories for the production of CH 2 (a 1 A 1 ) + CO(X 1 Σ + ) and CH 2 (X 3 B 1 ) + CO(X 1 Σ + ). Our prediction for the primary product CH 2 (a 1 A 1 ) + CO(X 1 Σ + ) formation is in good agreement with earlier experimental results. The pressure independent rate constant for this channel can be expressed by k 1 (T) = 8.62 × 10 –11 T 0 .16 exp(–20/T) cm 3 molecule –1 s –1 . For the production of CH 2 (X 3 B 1 ) + CO(X 1 Σ + ), the rate constant k 2 can be represented as k 2 (T) = 7.63 × 10 –16 T 1.56 exp(–386/T) cm 3 molecule –1 s –1 . The predicted product branching ratios for the reaction are in close agreement with experimental data as well. We also predicted the heat of formation at 0 K for 2 HCCO, 3 CCO, and 1 CCO by CCSD(T)/6-311++G(3df,2p), CBS-QB3, and G2M; the values are in good agreement among one another. Specifically, the CCSD(T) values are: Δ f H°(HCCO, X 2 A″) = 42.52 ± 0.70; Δ f H°(CCO, X 3 Σ g ) = 91.50 ± 0.54; and Δ f H°(CCO, a 1 Δ) = 110.22 ± 0.54 kcal/mol.
- Gas phase reactions
- Hydrocarbon combustion
- Ketenyl radical (HCCO)
- Quantum-chemical calculations