Density Functional Theory and MP2 methods, with a variety of basis sets, were used to compute reactant and transition state structures for the unimolecular 1,2-HF and 1,2-HCl elimination reactions of CF3CH2CCl3, CH3CH2CCl3, and CH3CCl3. These approaches result in threshold energies that vary as much as 10 kcal/mol depending on the specific method and basis set; however, the vibrational frequencies and moments of inertia are relatively consistent regardless of the computational method employed. Thus, the frequencies and moments of inertia were used with statistical rate constant calculations to match computed and experimental rate constants to give reliable threshold energies for the CF3CH2CCl3, CH3CH2CCl3, and CH3CCl3 systems. The most reliable computational methods for these elimination reactions will be discussed.
