The potential energy surface for the reaction of the ketenyl radical (HCCO) with O{sub}2 is characterized with a combination of density functional, Moller Plesset perturbation and coupled cluster theories. Trajectory simulations, employing directly determined density functional force fields, are used to explore the mechanism further. Variational transition state theory based master equation simulations, implementing the quantum chemically determined molecular properties, provide estimated product state distributions and rate constants. For all temperatures considered here (300-2500 K), the dominant products are CO{sub}2+CO+H independent of pressure up to 100 atm, thereby explaining the coincident formation of CO{sub}2 and CO in the oxidation of acetylene. These products arise primarily from the decomposition of the initial OOCHCO adduct via the formation of a four-membered OCCO ring, followed by, in succession, the splitting of the OO, the CC, and the CH bonds. At low temperatures, the modest barrier in the entrance channel, which arises from the need to break the resonances in the reactants prior to bond formation, provides the rate-limiting transition state. A variational treatment of this transition state reduces the calculated rate coefficient relative to conventional transition state theory by ～35%. At higher temperatures, the formation of the four-membered ring becomes a rate-limiting step, even though this process is essentially barrierless. An OCHCO+O channel becomes increasingly important with increasing temperature, but still contributes only about 10% at 2500 K. The direct dynamics simulations indicate that various H transfers may occur during the final dissociation steps, primarily to yield CO+CO+OH with an overall branching ratio of about 9%. A downward adjustment by 3.2 kcal/mol of the HCCO+O{sub}2 entrance barrier results in total rate coefficients that are in good agreement with experiment. The predicted channel-specific rate coefficients are then 7.94×10{sup}(-12)T{sup}(-0.142) exp(-1150/RT)(CO{sub}2+CO+H), 3.62×10{sup}(-22)T{sup}(2.69) exp(-3541/RT)(OCHCO+O), and 3.17×10{sup}-13T{sup}(-0.020) exp(-1023/RT)(CO+CO+OH) cm{sup}3 molecule{sup}-1 s{sup}-1, where R= 1.987 cal mol{sup}-1 K{sup}-1.
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机译：对于乙烯酮自由基（HCCO）与O- {子} 2的反应势能面的特征在于与密度泛函，莫勒Plesset微扰和耦合簇理论的组合。弹道的模拟，采用直接确定的密度泛函力场，用于进一步探索机制。基于变过渡态理论主方程的模拟，化学实现量子确定分子特性，提供估计的产品状态分布和速率常数。对于这里所考虑的所有的温度（300-2500 K），主导的产品是CO {子}的压力高达100 2 + CO + H独立大气压，从而说明的氧化CO {子} 2和CO的形成一致乙炔。这些产品主要出现从通过四元环OCCO的形成的初始OOCHCO加合物的分解，接着，连续的OO中，CC，和CH键的分裂。在低温下，适度阻挡在入口通道，这是由于需要打破共振在之前键形成反应物，提供的限速过渡状态。该过渡状态的变治疗降低相对于计算出的速率系数常规过渡态理论由〜35％。在较高的温度下，四元环的形成变得一个限速步骤，尽管这过程基本上barrierless。一个OCHCO + O信道变得随温度升高而日益重要，但仍处于2500 K的直接动力学模拟表明，在最后的解离步骤，可能会出现各种ħ转移不仅有助于约10％，主要是为了得到CO + CO + OH与约9％的总分支比。向下调整由3.2千卡的HCCO + O {子}中，其与实验一致总速率系数2入口屏障结果/摩尔。预测的信道特定的速率系数进行7.94×10 {SUP}（ - 12）笔{SUP}（ - 0.142）EXP（-1150 / RT）（CO {子} 2 + CO + H），3.62×10 { SUP}（ - 22）笔{SUP}（2.69）EXP（-3541 / RT）（OCHCO + O），和3.17×10 {SUP} -13T {SUP}（ - 0.020）EXP（-1023 / RT）（ CO + CO + OH）厘米{SUP} 3 {分子SUP} -1 S {SUP} -1，其中R = 1.987卡摩尔{SUP} -1 K {SUP} -1。
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