The geometries of the reactant, products, and transition state of the title reaction have been optimized at UHF, UMP2, and UMP4 levels with the double and triple zeta basis sets as well as polarization functions using the energy gradient method. The best potential barrier height for this reaction was calculated to be 9.05 kcal/mol with MP-SAC4 theory. The intrinsic reaction coordinate (IRC) was traced at UHF/6-31G and UMP2(FU)/6-311G(**) levels. The energy profile along the IRC was refined with subsequent MP-SAC4// MP2 calculations using UMP2(FU)/6-311G(**) geometries. The vibration modes and the couplings between the IRC and the normal modes were analyzed along the IRC. The calculated rate constants at the level of MP-SAC4//MP2 theory are in good agreement with the most recent experimental values in the temperature range from 2200 to 2800 K.