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用 Gaussian98程序包中的 AM1法 ,通过 UHF计算对模拟设计的 2 ,4-二甲基苯系列化合物的 5种热解途径进行了量子化学理论研究。计算结果表明 :卤素的存在对本系列化合物甲基 C— H键的热解断裂难易有影响且表现为“二分组效应”,即 F,Cl对苯环上甲基 C— H键有热活化作用 ,而 Br,I有热稳定作用 ,但差异不大。对于 C— X键 ,当卤素原子是 Cl与 I时 ,卤代苯上的 C— X键的热反应活性大于甲基上的 C—H键。对以上结果从优化的几何构型、自由基的生成焓及相对总能量上进行了分析 ,且得到相一致结果。
Quantum chemistry theory was used to study the five pyrolysis routes of 4, 4-dimethylbenzene compounds designed by AMF method in Gaussian98 package by UHF calculations. The calculation results show that the presence of halogen has an effect on the pyrolysis cracking of methyl C-H bonds of this series of compounds and appears as a “two-grouping effect”, that is, F and Cl have thermal activation on the methyl C- Role, and Br, I have thermal stability, but little difference. For the C-X bond, when the halogen atom is Cl and I, the thermal reactivity of the C-X bond on the halogenated benzene is greater than the C-H bond on the methyl group. The above results were analyzed from the optimized geometry, the formation enthalpies of free radicals and the relative total energies, and the consistent results were obtained.