Reactivity of hydrogen abstraction in CH2Cl2 by CHX− (X = F, Cl, Br, I) from a theoretical viewpoint

The H-abstraction reactions of CHX− (X = halogen) with CH2Cl2 have been investigated in detail using ab initio theoretical method. Optimized geometries and frequencies of all stationary points on PES are obtained at the MP2/6-311++G(d, p)/RECP level of theory, and then the energy profiles are refined at the QCISD(T)/6-311++G(3df, 2p)/RECP by using the MP2/6-311++G(d, p)/RECP optimized geometries. Our calculated findings suggest that the reactivity of the title reactions presents an increasing trend CHI− + CH2Cl2 < CHBr− + CH2Cl2 < CHCl− + CH2Cl2 < CHF− + CH2Cl2. This result was further analyzed by the NBO charges, the Activation Strain model and the correlations of activation barrier with both PA and IE, respectively. As an additional study, it is found that the entropy has little effect on the reactivity of the H-abstraction reactions.