Theoretical study of the gas-phase S(N)2 reactions of X- with CH3OY (X, Y=Cl, Br, I)

摘要

The gas-phase nucleophilic substitution reactions at saturated oxygen X- + CH3OY (X, Y Cl, Br, I) have been investigated at the level of CCSD(T)/6-311+G(2df,p)//B3LYP/6-311+G(2df,p). The calculated results indicate that Xpreferably attacks oxygen atom of CH3OY via a S(N)2 pathway. The central barriers and overall barriers are respectively in good agreement with both the predictions of Marcus equation and its modification, respectively. Central barrier heights (Delta H-XY(not equal) and AH(YX)(not equal)) correlate well with the charges (Q) of the leaving groups (Y), Wiberg bond orders (BO) and the elongation of the bonds (O-Y and O-X) in the transition structures. (c) 2006 Wiley Periodicals, Inc.