CH_2FCHF_2与富氧自由基HOOO反应机理的理论分析

Theoretical Study on the Mechanism of the Reaction of CH_2FCHF_2 with HOOO

采用密度泛函理论方法研究了富氧自由基HOOO与CH2FCHF2分子的反应机理.用MPW1K和BHandHLYP方法结合6-31+G(d,p)基组优化了反应势能面上各驻点的几何构型.用内禀反应坐标(IRC)计算和频率分析方法对过渡态进行了验证.对所有的驻点进行了CCSD/6-31+G(df,p)∥MPW1K/6-31+G(d,p)的单点能量计算.CH2FCHF2分子具有的2种构象分别指定为CH2FCHF2-a,CH2FCHF2-b.结果表明:当HOOO进攻CH2FCHF2-a时有2条分支路径,其中HOOO进攻CH2F基团中H原子时发生的反应为最可几反应机制;当HOOO进攻CH2FCHF2-b时,HOOO抽取CHF2基团中H的通道的反应势垒比HOOO抽取CH2F基团中H的通道的势垒低,即生成物CH2FCF2为此反应中的主要产物.

In this paper,the reaction mechanism of CHzFCHFz with H OOO was studied using the density functional theory （DFT） at the BHandHLYP/6-31＋ G（d, p） and MPW1K/6-31＋ G（d, p） levels of theory.The geometries for the reactants, transition states and products were completely optimized.The transition states all were verified by the vibration analysis and the intrinsic reaction co- ordinate （IRC） calculations.In order to obtain more accurate energies, the energies of all of the stationary points were refined at a higher level CCSD/6-31 ＋ G （df, p）//MPW1 K/6-31 ＋ G（ d, p）. Two conformers were located as CH2 FCHF2 -a and CHzFCH Fz -b.The results of calculation show that the CHz F group of CHzFCHFz-a molecule is a highly reactive site.For the reaction of CHzFCHFz-b with HOOO,the H abstraction by HOOO from CHFz group is dominant with the smaller potential barrier.Consequently,it could be anticipated that CHzFCFz may be the main product in the reaction of HOOO with CHzFCHF2-b.