Elementary gas phase reaction of hydrogen peroxide with fluorine atom has been investigated theoretically using ab initio quantum chemistry methods. Two possible reaction paths are considered: the H-abstraction path leading to HO 2 and HF products and the OH-abstraction one leading to OH and HOF products. The optimized structures and the harmonic vibrational frequencies of all the involved molecular systems are calculated using the CCSD(T) approach with the jun-cc-pvtz basis set. For the H-abstraction path, the reaction is found to be barrier less with a ZPE corrected classical barrier height equals to-2.5 kcal mol-1. A reactant complex (RC) is located at the entrance channel with relative stabilities about 3.8 and 1.3 kcal.mol-1 compared to the reactants (H 2 O 2 + F) and the transition state (TS), respectively. These results suggest that the reaction according to this path is very fast, which can explain the remarkable lack in the corresponding kinetic experimental data. For the OH-abstraction path, the barrier height including ZPE correction is found to be 14.6 kcal mol-1. The corresponding rate constants k evaluated by means of the transition state theory TST over the temperature range of 200-2500 K shows that this path has no significant contribution to the title reaction.

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