Computational Investigation on the Formation and Decomposition Reactions of the C4H3O Compound (original) (raw)

Gas-phase mechanism and kinetics of the formation and decomposition reactions of the C 4 H 3 O compound, a crucial intermediate of the atmospheric and combustion chemistry, were investigated using ab initio molecular orbital theory and the very expensive coupled-cluster CCSD(T)/CBS(T,Q,5)//B3LYP/6-311++G(3df,2p) method together with transition state theory and Rice−Ramsperger−Kassel−Macus kinetic predictions. The potential energy surface established shows that the C 3 H 3 + CO addition reaction has four main entrances in which C 3 H 3 + CO → IS1-cis (CHCCH 2 CO) is the most energetically favorable channel. The calculated results revealed that the bimolecular rate constants are positively dependent on both temperatures (T = 300−2000 K) and pressures (P = 1−76,000 Torr). Of these values, the k 1 rate constant of the C 3 H 3 + CO → IS1-cis addition channel is dominant over the 300−2000 K temperature range, increasing from 1.53 × 10 −20 to 1.04 × 10 −13 cm 3 molecule −1 s −1 with the branching ratio reducing from 62% to 44%. The predicted unimolecular rate coefficients in the ranges of T = 300−2000 K and P = 1−76,000 Torr revealed that the intermediate products IS1cis, IS1-trans, and IS2 are rather unstable and would rapidly decompose back to the reactants (C 3 H 3 + CO), especially at high temperatures (T > 1000 K). The high-pressure limit rate constants for the C 4 H 3 O decomposition leading to products (C 3 H 3 + CO), (CHCCHCO + H), and (CHCO + C 2 H 2) have been found to be in excellent agreement with the available literature values proposed by Tian et al. (Combust. Flame, 2011, 158, 756−773) without any adjustment from the ab initio calculations. Therefore, the predicted temperature-and pressure-dependent rate constants can be confidently used for modeling CO-related systems under atmospheric and combustion conditions.