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运用 Gaussian 98程序包中的 AM1方法，对间二甲苯系列化合物的热反应活性及热裂解机理进行了研究。通过不同温度下标准热力学量的计算和自由基间的轨道能级差的量子化学理论计算，结果表明：（ 1）当温度低于 800℃时 ,对各反应物来说热力学支持的主反应路径均是苯环上甲基 C H键首先断裂。当温度达到 800℃时 ,热裂解路径由首先选择 C H键的断裂变成首先选择苯环与甲基间 C C键的断裂。该结论与实验结果一致；（ 2）各反应物之间的热反应活性由大到小的顺序为： 2,4二甲基苯酚 > 2,4二甲基 1巯基苯 >间二甲苯 > 2,4二甲基 1氰基苯。同时亦说明，自由基之间的前线轨道能级差和热力学量的变化等理论参数一样亦可用于判断间二甲苯系列反应物的热解机理和热反应活性。
The thermal reactivity and thermal cracking mechanism of m-xylene series compounds were studied by AM1 method in Gaussian 98 package. Through the calculation of the standard thermodynamic quantities at different temperatures and the quantum chemical theory of the difference in orbital energy levels between the free radicals, the results show that: (1) when the temperature is below 800 ° C, the thermodynamic support for all reactants Is a methyl benzene CH bond first broken. When the temperature reaches 800 ℃, the pyrolysis path changes from the first choice of the C H bond to the first choice of the C-C bond break between the benzene ring and the methyl group. The conclusion is consistent with the experimental results. (2) The order of thermal reactivity between reactants is as follows: 2,4-dimethylphenol> 2,4-dimethyl-1-mercaptobenzene> m-xylene> 2 , 4 dimethyl 1 cyanobenzene. At the same time, it also shows that theoretical parameters such as the energy difference between the frontier orbital of free radicals and the change of the thermodynamic quantities can also be used to judge the pyrolysis mechanism and the thermal reactivity of m-xylene series reactants.