The oxidation of CH₂CO by (¹Δ_g) O₂ has been investigated by means of high level quantum chemical and chemical kinetic calculations. The reaction was found to proceed through a four-membered cyclic transition state resulting from the addition of O₂ to the CC bond of ketene. The reaction energetics has been calculated employing post-CCSD(T) corrections. The energy of the transition state was found to be 33.6 kcal mol⁻¹ below that of the isolated reactants. The rate coefficient, calculated using master equations under tropospheric conditions, was found to be 5.1 × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹ at 298 K and 1 bar. Atmospheric implications of the title reaction have been estimated by comparing the atmospheric lifetime of ketene for the title reaction against reactions with ˙OH, H₂O and NH₃. On a global scale, the lifetime for the title reaction was found to be almost 70 times that for the reaction with ˙OH. However, under special conditions, where the local concentration of singlet O₂ is significantly higher and/or the concentration of ˙OH is significantly lower, singlet O₂ initiated oxidation could become the most significant tropospheric loss mechanism of CH₂CO.

中文翻译：

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单线态 （1Δg） O2 引发气相氧化，成为乙烯酮的潜在对流层衰变通道


CH₂CO 被 （¹Δ_g） O₂ 氧化的研究是通过高级量子化学和化学动力学计算进行的。发现该反应通过四元环状过渡态进行，这是由于在乙烯酮的 CC 键上添加了 O₂ 而产生的。反应能量学是使用 CCSD（T） 后校正计算的。发现过渡态的能量比分离反应物的能量低 33.6 kcal ^mol-1。在对流层条件下使用主方程计算的速率系数发现，在 298 K 和 1 bar 时，速率系数为 5.1 × ^10-15 cm³ 分子^{-1 s-1}。通过比较标题反应与与 ̇OH、H₂、O 和 NH₃ 反应的乙烯酮的大气寿命，估计了标题反应的大气影响。在全球范围内，研究发现标题反应的寿命几乎是与 ̇OH 反应的 70 倍。然而，在特殊条件下，单线态 O₂ 的局部浓度明显较高和/或 ̇OH 浓度显著降低，单线态 O₂ 引发的氧化可能成为 CH₂CO 最显著的对流层损失机制。