Hydrogen abstraction reaction between N(~4S) and CH_3X (X = H, F, Cl) is explored using the B3LYP method. Optimized geometries and harmonic frequencies of reactants, products and transition states are obtained. The 6-31G(d), 6-311+G(d,p) and 6-311++G(2d, 2p) basis sets are employed in present calculations, in order to investigate effects of the size of the basis sets. Results show that the activation barriers and reaction endothermic values are reduced with increasing of the basis sets. Additionally, compared with reactions involving CH_4, CH_3F and CH_3Cl, the present results suggest that the inductive effect of halogen atom lowers the activation barrier for hydrogen abstraction.

Key words: NITROGEN ATOM, HALOHYDROCARBON, METHANE P, TRANSITION STATE