2,4-二甲基卤代苯热解机理的理论研究

A theeretical study on pyrolysis mechanism of a series of compounds 2,4-Dimethylhalogenbenzene

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。

Pyrolysis mechanism about a series of 2,4 dimethylhalogenbenzene compounds (the compounds with different halogen on the benzene ring, including -F,-Cl,-Br,-I) is studied by using the AM1 method in Gaussian 98 program package, and 5 types of pyrolysis processes are established and are calculated. The results show that the pyrolysis reaction of breaking methyl′s C-H bond on the benzene ring is affected by different halogen on the benzene ring. When halogen is -F or -Cl, the methyl′s C-H bond has hot activation. The methyl′s C-H bond has hot stabilization when it is -Br or -I. Which exhibit 'Dichotomous grouping effect'. Meanwhile, for C-X bond, when X is Br or I atom, broken C-H is more difficult than broken C—X bond.