Bondline / Reactions

Aldol condensation (E1cB)

On heating, the aldol product loses water: base forms the enolate, which then pushes out hydroxide (E1cB). The product is a conjugated enone or enal.

Enolates · 2 steps

Conditions

NaOH, heat.

Mechanism in 2 steps

Red curly arrows show where each pair of electrons moves.

HO−OOHHO−OH+
Step 1Hydroxide removes the acidic α-proton, giving an enolate.
O−OHOHO−+
Step 2The enolate reforms C=O and expels hydroxide from the β-carbon (E1cB).

About enolates reactions

A C–H next to a carbonyl is acidic, because the anion formed (an enolate) is stabilised by resonance. Enolates are carbon nucleophiles that make new C–C bonds.

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