Quantum Chemistry Research of Pyrolysis Mechanism of Carbon Matrix Precursor
碳前驱体热解机理的理论研究──反应能量、自由基的轨道能级及相对稳定性

Standard enthalpy change, free energy change, entropy change, the frontier orbital energy and relative stability of free radicals about the 8 types of design pyrolysis processes of the series of m-xylene compounds were calculated by the AM1 method in Gaussian 98 program package. The results show that the pyrolysis process of these compounds first starts from the C--H bonds of the methyls on the benzene rings. This conclusion is in accord with the experimental result. The activity sequence of the series of m-xylene compounds is C8H9OH(d1)>C8H9SH(d2)>C8H10(a)>C8H9-CN(d3). At the same time, it is also proved that the frontier orbital energy difference and the relative stability of these free radicals are the same as the thermodynamics parameters, so that they can be used to the study of the pyrolysis mechanism and thermoreactive activity of this series of xylene compounds.