Effects of CF3 and CH3 Groups on the Threshold Energy for the Unimolecular Interchange Reaction of Cl- and F-Atoms in CF3CHFCH2Cl and CH3CHFCH2Cl

被引:6
作者
McClintock, Corey E. [1 ]
Smith, Kylie C. [1 ]
Heard, George L. [1 ]
Setser, D. W. [2 ]
Holmes, Bert E. [1 ]
机构
[1] Univ N Carolina, Dept Chem, Asheville, NC 28804 USA
[2] Kansas State Univ, Manhattan, KS 66506 USA
基金
美国国家科学基金会;
关键词
PHASE PYROLYSIS KINETICS; 1,2-FCL REARRANGEMENT; RATE CONSTANTS; ELIMINATION; ALKYL; ISOMERIZATION; HCL; HF; ENTHALPIES; ASSIGNMENT;
D O I
10.1021/jp412299p
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The recombination reactions of CH2Cl radicals with CF3CHF and with CH3CHF radicals were used to generate CF3CHFCH2Cl and CH3CHFCH2Cl molecules with 90-92 kcal mol(-1) of vibrational energy. The experimental rate constants for elimination of HCl and HF and the interchange of Cl and F atoms were measured and compared to RRKM calculated rate constants to assign the threshold energy for each unimolecular reaction channel. The Cl/F interchange reaction is approximately 18% of the total unimolecular reaction for both molecules. The product branching ratios and some rate constants also could be measured for the unimolecular reactions of the rearranged molecules, CF3CHClCH2F and CH3CHClCH2F. The most important result is that the CH3 group lowers the threshold for Cl/F interchange relative to CH2FCD2Cl, as expected for an electron-density donating group, and the CF3 group, an electron-density withdrawing group, increases the threshold energy relative to CH2FCD2Cl. The CH3 and CF3 groups alter the threshold energies of the HCl and HF elimination reactions in such a way so as to maintain the same branching fraction for the interchange reaction. The results from density functional theory using the B3PW91 method with the 6311+G(w2d,p) and G-31G(d',p') basis sets are used to discuss the trends in threshold energies for the Cl/F interchange and the HF and HCl elimination reactions.
引用
收藏
页码:2886 / 2896
页数:11
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