Ab initio direct dynamic study on the reaction Br atoms with CH3Br

By means of direct dynamics methods, theoretical investigations are carried out on the multiple-channel reaction Br + CH3Br. The minimum energy path are calculated at the MP2/6-311+G(d, p) level, and energetic information is further refined at the QCISD(T)/6-311+G(3df, 2p) (single-point) level. The rate constants for H-abstraction channel is calculated by canonical variational transition state theory with small-curvature tunneling contributions over the wide temperature region 200-3000 K. The theoretical three-parameter expression of reaction (R1) is given as k1 = 1.05 × 10−17T2.43exp(−5510.86/T) (in cm3 molecule−1 s−1). For the title reaction, H-abstraction channel leading to the formation of CH2Br + HBr is the predominant channel.