Computational Insights into SN2 and Proton Transfer Reactions of CH3O- with NH2Y and CH3Y

Bimolecular nucleophilic substitution (S(N)2) reactions have been extensively studied in both theory and experiment. While research on C-centered S(N)2 reactions (S(N)2@C) has been ongoing, S(N)2 reactions at neutral nitrogen (S(N)2@N) have received increased attention in recent years. To recommend methods for dynamics simulations, the comparison for the properties of the geometries, vibrational frequencies, and energies is done between MP2 and six DFT functional calculations and experimental data as well as the high-level CCSD(T) method for CH3O-+NH2Cl/CH3Cl reactions. The relative energy diagrams at the M06 method for CH3O- with CH3Y/NH2Y reactions (Y=F, Cl, Br, I) in the gas and solution phase are explored to investigate the effects of the leaving groups, different reaction centers, and solvents. We mainly focus on the computational of inv-S(N)2 and proton transfer (PT) pathways. The PT channel in the gas phase is more competitive than the S(N)2 channel for N-center reactions, while the opposite is observed for C-centered reactions. Solvation completely inhibits the PT channel, making S(N)2 the dominant pathway. Our study provides new insight into the S(N)2 reaction mechanisms and rich the novel reaction model in gas-phase organic chemistry.