Benchmark values for the reaction enthalpy (298 K) and the barrier height (0 K) of the reaction, CF3CHFCF3 + F → CF 3CFCF3 + HF, have been calculated at state-of-the-art ab initio level to be -34.7 ± 1.0 and -0.9 ± 0.9 kcal/mole, respectively. The B3LYP, BH&HLYP, BB1K, MPW1K, MPWB1K and TPSS1KCIS functionals and the model method, the integrated molecular orbital + molecular orbital (IMOMO) method, have also been used to study this reaction. ; Department of Building Services Engineering