C2(a^3Πu)自由基与若干不饱和碳氢化合物反应的温度效应

Temperature Dependence of Reactions of C_2(a^3Π_u) Radical with Several Unsaturated Hydrocarbons

运用脉冲激光光解-激光诱导荧光(PLP-LIF)的方法研究了C2(a3Πu)自由基与若干不饱和碳氢化合物(C2H4(k1),C2H2(k2),C3H6(k3)和2-C4H8(k4))气相反应的温度效应.在298-673 K的温度范围内,获得了这些反应的双分子反应速率常数.获得的速率常数可以用Arrhenius公式表达如下:k1(T)=(4.53±0.05)×10-11exp[(196.41±5.20)/T],k2(T)=(3.94±0.04)×10-11exp[(143.04±4.28)/T],k3(T)=(7.96±0.17)×10-11exp[(185.10±8.86)/T],k4(T)=(1.04±0.02)×10-10exp[(180.34±7.67)/T],误差为±2σ.由获得的双分子反应速率常数及其所呈现的负温度效应,在298-673 K温度范围内,C2(a3Πu)自由基和这些不饱和碳氢化合物的反应遵循加成机理.

We studied the temperature dependence on the gas phase reactions of the C2（a3Πu） radical with several unsaturated hydrocarbons（C2H4（k1）,C2H2（k2）,C3H6（k3）,and 2-C4H8（k4）） by means of pulsed laser photolysis-laser induced fluorescence（PLP-LIF） technique.The bimolecular rate constants for these reactions were obtained in the temperature range of 298-673 K.The obtained kinetics data were used to derive the following Arrhenius expressions： k1（T）=（4.53±0.05）×10-11exp[（196.41±5.20）/T],k2（T）=（3.94±0.04）×10-11exp[（143.04±4.28）/T],k3（T）=（7.96±0.17）×10-11 exp[（185.10±8.86）/T],and k4（T）=（1.04±0.02）×10-10exp[（180.34±7.67）/T],where all error estimates are ±2σ and represent the precision of the fit.The observed bimolecular rate constants along with the negative temperature dependences of k（T） allow us to reach a conclusion that the reactions of C2（a3Πu） with these unsaturated hydrocarbons in the temperature range of 298-673 K proceed via an addition mechanism.