环己烷的热裂解机理

用Gaussian 98程序包中AM1法和DFT方法，对液相沉积法制碳/碳（C/C）复合材料的碳源化合物环己烷的热解机理做了量子化学理论研究.通过对化合物6种可能的热裂解路径的热力学和动力学计算，找到了环己烷热裂解的主反应路径.结果表明：(1) AM1与DFT计算均显示，断裂C－C键，最终生成乙烯和2 丁烯的反应通道是环己烷的主要裂解通道，与质谱数据吻合; (2) 除主反应路径外,余下的由易到难生成化合物的顺序为甲基环戊烷 >环己烯 >4 甲基环戊烯 >1，3 丁二烯; (3) AM1方法可以很好地推测较大分子体系的热裂解机理，而DFT方法计算的热力学量更接近实验数据.

Pyrolysis Mechanism of Cyclohexane

By using AM1 and DFT methods in Gaussian 98 program package, quantum chemistry theoretical research was carried out for the pyrolysis mechanism of cyclohexane, used as carbon matrix compound for preparing carbon/carbon composition material with the rapid chemical liquid deposition method. Reaction paths studied are showed as scheme at p355. By thermodynamic and kinetic calculations of six possible pyrolysis channels, the main reaction channel was found. (1) confirmed by both AM1 and DFT calculation results,the main pyrolysis reaction channel is the breaking of C－ C bond firstly, followed by a series of intermediates,and finally the productiom of ethene and 2-butene. That is reaction channel(2b),which is in accordance with the mass-spectrometric data. (2) Except for the main pyrolysis channel, the order of producing final products from the easiest to the most difficult ones is methylcyclopentane >cyclohexene >4-methylcyclopentene >1,3-butadiene. This is supported by results of thermodynamic and kinetic calculation. (3) AM1 method is recommended to study the pyrolysis mechanism of larger molecular systems, while the thermodynamic data computed by DFT method coincide better with the experimental results.