过氧硝酸乙酰酯分解反应的速率常数

Theoretical Studies of the Rate Constants for Peroxyacetyl Nitrate Decomposing to CH_3C(O)O+NO_3

在G3MP2B3结构优化和能量计算的基础上,采用RRKM理论和疏松过渡态模型重新估算了过氧硝酸乙酰酯(PAN)的热分解反应PAN→CH3C(O)OO+NO2(R1)的反应速率常数,得到与实验值吻合的结果.用同样的模型计算了PAN→CH3C(O)O+NO3(R2)的反应速率常数.结果表明,在相同的反应条件下,R1是主要的分解通道,R2是次要通道,R2的反应速率常数比R1的小两个数量级.

The rate constants for the thermal decomposition reaction of peroxyacetyl nitrate （PAN）, PAN→CHaC（O）OO＋ NO2（R1） were reestimated by RRKM theory and loosing transition state model based on the optimized structures and energies at the G3MP2B3 level of theory and the results agree with the experiment values. Then using the same models, the rate constants for another thermal decomposition reaction of PAN, PAN→Ha（O）O＋NOa（R2） were studied. In Troe＇s notation, the RRKM curves are presented by the following expressions for the limiting low- and highpressure rate constants, k0（1）=8.0×10^-3 exp[-11912.8/T] cm^3·molecule^-1· s^-1; k∞（1）=2.8×10^16 exp[-13531.8/T] s^-1; k0（2）= 6.1 ×10^16 exp[-13011.9/T] cm^3· molecule^-1· s^-1; k∞（2）=4.0×10^16 exp[-15463.1/T] s^-1. The results of calculation suggested that the reaction R1 is the main dissociation channel, while R2 is the minor one and the difference between the rates of the two reactions is about 10^2 at the same conditions.