CH_(4-n)F_n(n=1~3)与CH_3氢抽提反应微观动力学的理论研究  

Micro-dynamics of Hydrogen Abstraction Reaction Between CH_(4-n)F_n (n=1—3) and CH_3

作　　者：冯丽霞[1] 王文亮[1] 李琳[1] 王渭娜[1] 罗琼[1] 李前树[1] 

机构地区：[1]陕西师范大学化学与材料科学学院,西安710062

出　　处：《高等学校化学学报》2006年第9期1733-1737,共5页Chemical Journal of Chinese Universities

基　　金：陕西省自然科学基金(批准号:2003B05)资助

摘　　要：采用量子化学的QCISD（T）／6-311＋G（d，P）／／BHandHLYP／6—311G（d，P）方法研究了氟代甲烷CH4-nFn（n=1～3）与CH，自由基氧抽提反应的微观动力学性质．并利用Polyrate程序分别计算了3个反应在200～3000K范围内的速率常数．计算结果表明，R1a，R2a和R3三个反应路径的反应能量分别为-12．7，-9．5和11．8kJ／mol，相应的能垒依次为67．0，62．2和67．5kJ／mol．在437K时，k^CVT/SCT分别为6．72×10^-19，8．01×10^-18和8．82×10^-20cm^3／（molecule·s）．计算结果还表明，在低温段反应的量子隧道效应显著，在计算温度范围内变分效应对反应速率常数的影响可以忽略．QCISD （T）/6-311 ＋ G （ d ,p ）//BHandHLYP/6-311 G （ d ,p ） method was employed to reveal the reaction mechanism and to predict the micro-kinetic character of the hydrogen abstraction reactions of CH4-nFn （ n = 1-3 ） with CH3. The rate constants of the reactions were evaluated by means of the canonical variational transition-state theory（CVT） conjunction with small-curvature tunneling （SCT） correction in the temperature range of 200-3 000 K. In this study, the reaction energies AE of Rla, R2a and R3 are - 12.7, -9.5 and 11.8 kJ/mol, the potential barriers △E^≠ were 67.0, 62.2 and 67.5 kJ/mol, respectively. At 437 K, the CVT/SCT rate constants were 6.72 × 10^-19, 8.01 × 10^-18 and 8. 82 × 10^ -20 cm^3/（molecule · s） , which were in agreement with the experimental values 3.31 × 10^-19, 1.05 × 10^ -18 and 8.33 × 10 ^-20 cm^3/（ molecule · s）. The results indicate that the tunneling effect was considerable at the lower temperatures, while the variational effect was almost negligible in the entire process.

关 键 词：CH4-nFn(n=1~3) 氢抽提反应 QCISD(T)//BHandHLYP 速率常数 

分 类 号：O641[理学—物理化学]