Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Renmin Road 5268, Changchun, Jilin 130024, People's Republic of China.
J Chem Phys. 2010 Feb 14;132(6):064301. doi: 10.1063/1.3292570.
The low-lying triplet and singlet potential energy surfaces of the O((3)P)+CH(3)CN reaction have been studied at the G3(MP2)//B3LYP/6-311+G(d,p) level. On the triplet surface, six kinds of pathways are revealed, namely, direct hydrogen abstraction, C-addition/elimination, N-addition/elimination, substitution, insertion, and H-migration. Multichannel Rice-Ramsperger-Kassel-Marcus theory and transition-state theory are employed to calculate the overall and individual rate constants over a wide range of temperatures and pressures. It is predicted that the direct hydrogen abstraction and C-addition/elimination on triplet potential energy surface are dominant pathways. Major predicted end products include CH(3)+NCO and CH(2)CN+OH. At atmospheric pressure with Ar and N(2) as bath gases, CH(3)C(O)N (IM1) formed by collisional stabilization is dominated at T<700 K, whereas CH(3) and NCO produced by C-addition/elimination pathway are the major products at the temperatures between 800 and 1500 K; the direct hydrogen abstraction leading to CH(2)CN+OH plays an important role at higher temperatures in hydrocarbon combustion chemistry and flames, with estimated contribution of 64% at 2000 K. Furthermore, the calculated rate constants are in good agreement with available experimental data over the temperature range 300-600 K. The kinetic isotope effect has also been calculated for the triplet O((3)P)+CH(3)CN reaction. On the singlet surface, the atomic oxygen can easily insert into C-H or C-C bonds of CH(3)CN, forming the insertion intermediates s-IM8(HOCH(2)CN) and s-IM5(CH(3)OCN) or add to the carbon atom of CN group in CH(3)CN, forming the addition intermediate s-IM1(CH(3)C(O)N); both approaches were found to be barrierless. It is indicated that the singlet reaction exhibits a marked difference from the triplet reaction. This calculation is useful to simulate experimental investigations of the O((3)P)+CH(3)CN reaction in the singlet state surface.
O((3)P)+CH(3)CN 反应的低位三重态和单重态势能面已在 G3(MP2)//B3LYP/6-311+G(d,p)水平上进行了研究。在三重态表面上，揭示了六种途径，即直接氢提取、C 添加/消除、N 添加/消除、取代、插入和 H 迁移。多通道 Rice-Ramsperger-Kassel-Marcus 理论和过渡态理论被用来计算在很宽的温度和压力范围内的总速率常数和各个速率常数。预测直接氢提取和三重态势能面上的 C 添加/消除是主要途径。主要预测的最终产物包括 CH(3)+NCO 和 CH(2)CN+OH。在大气压下，Ar 和 N(2)作为浴气体，T<700 K 时主要由碰撞稳定化形成 CH(3)C(O)N (IM1)，而 800-1500 K 温度范围内由 C 添加/消除途径生成的 CH(3)和 NCO 是主要产物；在碳氢化合物燃烧化学和火焰中，高温下直接氢提取导致 CH(2)CN+OH 发挥重要作用，在 2000 K 时估计贡献为 64%。此外，在 300-600 K 的温度范围内，计算得到的速率常数与可用的实验数据吻合良好。还计算了三重态 O((3)P)+CH(3)CN 反应的动力学同位素效应。在单重态表面上，氧原子可以容易地插入 CH(3)CN 的 C-H 或 C-C 键中，形成插入中间体 s-IM8(HOCH(2)CN)和 s-IM5(CH(3)OCN)，或者加成到 CH(3)CN 的 CN 基团的碳原子上，形成加成中间体 s-IM1(CH(3)C(O)N)；这两种方法都没有势垒。表明单重态反应与三重态反应有明显的不同。此计算对模拟 O((3)P)+CH(3)CN 反应在单重态表面的实验研究很有用。
