High-Temperature Experimental and Theoretical Study of the Unimolecular Dissociation of 1,3,5-Trioxane.
High-Temperature Experimental and Theoretical Study of the Unimolecular Dissociation of 1,3,5-Trioxane.
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DOI：
10.1021/acs.jpca.5b01801
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发表时间：
2015-06
期刊：
影响因子：
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通讯作者：
A. Alquaity;B. Giri;J. Lo;A. Farooq
中科院分区：
文献类型：
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作者：
A. Alquaity;B. Giri;J. Lo;A. Farooq
在实验和理论上研究了1，3，5-三恶烷的单分子解离。实验是在775-1082 K的温度范围和900 Torr附近的压力下，使用高重复率飞行时间质谱仪（TOF-MS）耦合到激波管（ST）的反射激波后面进行的。对反应产物进行了直接鉴定，发现甲醛是1，3，5-三恶烷解离的唯一产物。反应速率系数提取的最佳拟合实验测得的浓度-时间的历史。此外，采用高水平量子化学和RRKM计算研究了1，3，5-三恶烷解离的衰减行为。在B3 LYP/cc-pVTZ、MP2/cc-pVTZ和MP2/aug-cc-pVDZ水平上计算了所有物种的分子几何构型和频率，而固定点的单点能量则采用包括三重激发微扰处理（CCSD（T））的耦合团簇单激发和双激发计算。据发现，发生的解离通过一个协调的机制，需要克服的能量势垒为48.3千卡/摩尔。新的实验数据和理论计算作为验证和扩展的动力学数据发表的其他小组。压力极限速率系数的计算值可表示为log 10 k∞（s（-1））= [15.84 -（49.54（kcal/mol）/2.3RT）]（500-1400 K）。
Unimolecular dissociation of 1,3,5-trioxane was investigated experimentally and theoretically over a wide range of conditions. Experiments were performed behind reflected shock waves over the temperature range of 775-1082 K and pressures near 900 Torr using a high-repetition rate time of flight mass spectrometer (TOF-MS) coupled to a shock tube (ST). Reaction products were identified directly, and it was found that formaldehyde is the sole product of 1,3,5-trioxane dissociation. Reaction rate coefficients were extracted by the best fit to the experimentally measured concentration-time histories. Additionally, high-level quantum chemical and RRKM calculations were employed to study the falloff behavior of 1,3,5-trioxane dissociation. Molecular geometries and frequencies of all species were obtained at the B3LYP/cc-pVTZ, MP2/cc-pVTZ, and MP2/aug-cc-pVDZ levels of theory, whereas the single-point energies of the stationary points were calculated using coupled cluster with single and double excitations including the perturbative treatment of triple excitation (CCSD(T)) level of theory. It was found that the dissociation occurs via a concerted mechanism requiring an energy barrier of 48.3 kcal/mol to be overcome. The new experimental data and theoretical calculations serve as a validation and extension of kinetic data published earlier by other groups. Calculated values for the pressure limiting rate coefficient can be expressed as log10 k∞ (s(-1)) = [15.84 - (49.54 (kcal/mol)/2.3RT)] (500-1400 K).