E1cB elimination reaction

An elimination reaction in which a base removes a proton to form a carbanion intermediate before a leaving group departs, producing a double bond.

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Carbanion: An anion in which a carbon atom bears a negative charge and a lone pair. This charged intermediate forms when the base removes a proton.
Brønsted–Lowry acid–base theory: A theory defining acids as proton donors and bases as proton acceptors. The first step is proton transfer from the substrate to a base.
E1 elimination: A unimolecular elimination that forms a carbocation before loss of a proton. E1 forms a positively charged intermediate, whereas E1cB forms a negatively charged one.
Aldol condensation: A carbon–carbon bond-forming reaction whose aldol products can lose water to form conjugated carbonyl compounds. Dehydration of many aldol products proceeds by E1cB when the anion is stabilized.
β-Hydroxy carbonyl compound: A carbonyl compound bearing a hydroxyl group on its beta carbon. Base-promoted dehydration can remove its alpha proton before hydroxide leaves.
Deprotonation: The removal of a proton from a molecule, usually by a base. It is the first step and creates the carbon-centered anion.
pKa: A logarithmic measure of an acid's tendency to donate a proton in solution. Relative pKa values help assess whether deprotonation can form the intermediate.
E2 elimination: A bimolecular elimination in which proton removal and leaving-group departure occur in one concerted step. E2 has no carbanion intermediate, unlike the stepwise E1cB pathway.
Claisen–Schmidt condensation: A crossed aldol condensation between an enolizable carbonyl compound and a non-enolizable aldehyde or ketone. Its β-hydroxy carbonyl products commonly dehydrate through carbanion-mediated elimination.
β-Dicarbonyl compound: A compound with two carbonyl groups separated by one carbon atom. Its central carbon can form a resonance-stabilized anion before elimination.