Gas-Phase Nucleophilic Substitution at Vinylic Carbon. The Effect of p-Accepting Substitutions.

초록

The gas-phase bimolecular nucleophilic substitutions of 1-substituted(Y)-1-haloethane with halide anion nucleophiles have been studied theoretically at B3LYP level with 6-311+G(d,p) basis set. For the reactions with Y = HC C- substituent, in-plane SN2 paths with inversion ( SN s ) are more favorable than out?of-plane SN2 paths with retension of configuration ( SN p ). However, the SN p paths are rather preferred for the reactions with a relatively stronger electron withdrawing substituent, Y = N C-, in all cases. It could be, therefore, expected that the relative preference between the SN s and SN p paths is changed by the electronic effects of Y- substituent, i.e., the stronger electron accepting Y- substituent is, the more favorable SN p path is. These results have been compared to those for the unsubstituted vinyl halides.