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• 作者：Corey E. McClintock ; Kylie C. Smith ; George L. Heard ; D. W. Setser ; Bert E. Holmes
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：April 24, 2014
• 年：2014
• 卷：118
• 期：16
• 页码：2886-2896
• 全文大小：417K
• 年卷期：v.118,no.16(April 24, 2014)
• ISSN：1520-5215

文摘

The recombination reactions of CH₂Cl radicals with CF₃CHF and with CH₃CHF radicals were used to generate CF₃CHFCH₂Cl and CH₃CHFCH₂Cl molecules with 90鈥?2 kcal mol^鈥? 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(2d,p) and G-31G(d鈥?p鈥? basis sets are used to discuss the trends in threshold energies for the Cl/F interchange and the HF and HCl elimination reactions.