Ab initio quantum chemical method and density functional theory (DFT) have been used to study the reaction mechanism of the C-H bond activation of methane by Br+. The geometries of reactants, intermediates, transition states, and products were optimized at the B3LYP/6-311++G(3df,3p) and MP2/6-311++G(3df,3p) levels. The G2M(+) methods were used to obtain more accurate energies. The results show that the reaction undergoes via three triplet endothermic pathways and two singlet exothermic reaction channels. The reaction is more likely to proceed through the singlet pathways. The mechanism proposed in the present work is in reasonable agreement with the known experimental facts. Our theoretical results indicate that the halogen cation, Br+, may be a potential catalyst for C-H bond activation of methane.

Key words: ab initio, density functional theory, G2M(＋) method, C—H activation of methane, reaction mechanism