用多声子迁移模型理论研究硝基甲烷的分解机理

摘要

基于多声子迁移模型理论分析了撞击诱导硝基甲烷单分子分解反应可能存在的合理的反应路径.发现:对最低三态和基态的分子选择门模式分别为407 cm-1,436 cm-1和482 cm-1,616 cm-1时,计算得到的相同时间长度上的能量迁移参数分别为5.43×105 J/mol?K,5.82×105 J/mol?K和8.22×105 J/mol?K,6.43×105 J/mol?K.而理论计算CH3 NO2分子从基态跃迁致最低三态所需能量为2.39×105 J/mol,最低三态分子从C-N键断裂分解为硝基和甲基所需活化能为3.69×105 J/mol;基态的CH3 NO2分子从C-N键断裂生成硝基和甲基所需能量为2.24×105 J/mol.因此,能量迁移能够提供足够的能量使CH3 NO2分子在基态或者在跃迁至最低三态后从C-N键断裂生成硝基和甲基.这个结论与实验报道的结论基本一致.%Studies of the first dissociation of nitro-methane following impact have produced less consistent re-sults. In the present paper the mechanism of the first decomposition of nitro-methane is investigated based on the model of the multi-phonon up-pumping. When the doorway mode is 482 , 616 cm-1 and 407 , 436 cm-1 for the lowest singlet and triplet states of nitro-methane respectively,the energy transfer parameter is 6. 43 × 105 J/mol?K, 8. 22 × 105 J/mol?K for the lowest singlet state of nitro-methane and 5. 43 × 105 J/mol?K, 5. 82 × 105 J/mol?K for the lowest triplet state of nitro-methane. The energy barrier of the lowest singlet state is on-ly 2. 24 × 105 J/mol, and energy gap between the lowest triplet state and the ground state is 2. 39 × 105 J/mol, the activation energy of the lowest triplet state is only 3. 69 × 105 J/mol. So, we consider that the transfer energy in the up-pumping process is enough to lead to the excitation of molecule. The same transfer energy is also e-nough to feed the decomposition reaction of the lowest triplet start by the reaction coordinate of C-N bond. This result is consistent with the experiment that the major path way of nitro-methane can be profiled as:CH3 NO2→CH3 +NO2.