Chemically activated CF3CH2CCl3 was prepared with approximately 92 kcal/mol of internal energy by the combination of CF3CH2 and CCl3 radicals. Mercury photosensitization was used to form the radicals by photolysis of CF3CH2I and CCl4 in quartz vessels using a low-pressure Hg lamp. The only unimolecular pathway observed for CF3CH2CCl3 was 1,2-HCl elimination and the experimental rate constant was 7 x 106 s-1. DFT calculations were done to determine the transition state structures and to predict the threshold energies (E0) for the HF and HCl elimination reactions. The threshold energies for HCl loss from CF3CH2CCl3 and CF3CH2CH2Cl will be compared to determine whether the trend of declining E0s with Cl for H substitution observed for CH3CH2Cl, E0 = 55 kcal/mol and CH3CHCl2, E0 = 52 kcal/mol continues when the third Cl is added.

Unimolecular rate constant and threshold energy for 1,2-HCl elimination from activated CF3CH2CCl3

246th National Meeting (2013)

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