The E1cB Reaction

Although E1 reactions typically involves a carbocation intermediate, the E1cB reactoin utilizes a carbanion intermediate. This reaction is generally utilized when a poor leaving group, such an and alcohol, is involved. This poor leaving group makes the direct E1 or E2 reactions difficult. This reaction is used later in a reaction called an aldol condensation.

The product of this β

-elimination reaction is an α,β-unsaturated aldehyde or ketone. Base-catalyzed elimination occurs with heating. The additional stability provided by the conjugated carbonyl system of the product makes some aldol reactions thermodynamically and mixtures of stereoisomers (E & Z) are obtained from some reactions.

Figure: General reaction for an E1cB condensation

Going from reactants to products simply

Figure: The E1cB example