Abstract: 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.

Key words: Carbon/carbon composition material, Carbon matrix compound, 　Cyclohexane, Pyrolysis mechanism, Quantum chemistry research