Elimination and addition reactions. Part 34. The effect of activating group and medium on leaving group rank in elimination from carbanions

Abstract

Ranking of leaving groups in 1,2-elimination from carbanions has been extended to cyano-activated systems and, in a few cases, to oxo-activated systems. The ranks are compared with those found earlier for sulphonyl-activated eliminations. The results suggest that there is little cleavage of the bond to the leaving group in the transition state for the process in which the leaving group is expelled; these conclusions are reinforced by the insensitivity of the rates of these reactions to change of solvent and to intervention in any degree of ion-association in the media studied.