Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), Onogawa, Tsukuba, Japan.
Phys Chem Chem Phys. 2011 Apr 7;13(13):6296-304. doi: 10.1039/c0cp01942a. Epub 2011 Feb 28.
On-the-fly quasi-classical trajectory calculations using the density functional method were carried out to investigate the dynamics of the HC(O)CO radical, formed by OH radical- and Cl atom-initiated reactions of glyoxal at 298 K. The energy difference between the A' HC(O)CO radical, formed immediately after H atom abstraction, and the most stable A″ HC(O)CO radical is estimated to be 6.0 kcal mol(-1). The surplus energy followed by relaxation from A' HC(O)CO to A″ HC(O)CO goes to internal energy of the nascent HC(O)CO radicals and causes prompt decomposition into HCO + CO. The average internal energy partitioned into the HC(O)CO radical is higher in the OH reaction than in the Cl reaction, in accordance with exothermicity of the reactions. A fraction of the nascent HC(O)CO radicals (91% for the OH reaction and 47% for the Cl reaction) promptly decomposes into HCO and CO within 2.5 ps. The remaining HC(O)CO radicals, which do not undergo prompt decomposition, decompose thermally or add with O(2) in the presence of O(2). I re-evaluated the previous two experiment results of the product yield ratio [CO]/[CO(2)] vs. O(2) in the Cl atom-initiated reaction, in light of the reaction mechanism involving prompt decomposition. The two results give 9.5 × 10(6) s(-1) and 1.08 × 10(7) s(-1) for the thermal decomposition rate and 47% and 41% for the fraction of prompt decomposition in the Cl atom-initiated reaction, in good agreement with the present trajectory calculation.
在 298 K 下，使用密度泛函方法进行的准经典轨迹计算，研究了由 OH 自由基和 Cl 原子引发的乙二醛反应生成的 HC(O)CO 自由基的动力学。H 原子提取后立即形成的 A'HC(O)CO 自由基和最稳定的 A″HC(O)CO 自由基之间的能量差估计为 6.0 kcal mol(-1)。从 A'HC(O)CO 松弛到 A″HC(O)CO 的剩余能量进入新生 HC(O)CO 自由基的内部能量，并导致迅速分解为 HCO + CO。与反应的放热性一致，在 OH 反应中，进入 HC(O)CO 自由基的平均内部能量高于 Cl 反应。在 2.5 ps 内，新生 HC(O)CO 自由基的一部分（OH 反应为 91%，Cl 反应为 47%）迅速分解为 HCO 和 CO。其余的 HC(O)CO 自由基，由于没有发生迅速分解，在存在 O(2)的情况下，会通过热分解或与 O(2)加成而分解。根据涉及迅速分解的反应机制，我重新评估了之前在 Cl 原子引发的反应中产物生成比[CO]/[CO(2)]与O(2)的两个实验结果。两个结果给出了 Cl 原子引发反应中热分解速率的 9.5 × 10(6) s(-1)和 1.08 × 10(7) s(-1)，以及迅速分解的分数为 47%和 41%，与本轨迹计算结果吻合较好。
