Aldol condensation is a very useful reaction in the field of chemistry. It is a “bond forming” reaction and thus has wide applications in the field of synthetic chemistry. Independently discovered by Wurtz and Borodin, it involves a neucleophilic addition of a ketone moiety to an aldehyde molecule. This finally results into the synthesis of a ?-hydroxy ketone. Sometimes the ?-hydroxy ketone loses a molecule of water to give ?,?-unsaturated ketone. This reaction is called aldol condensation.

Aldehydes posessing atleast 1 Hydrogen atom is partially converted to its enolate anion by bases such as hydroxide and alkoxide ions.

Because the pKa’s of the aldehyde and water are similar, the solution contains signifi-
cant quantities of both the aldehyde and its enolate. Moreover, their reactivities are com-
plementary. The aldehyde is capable of undergoing nucleophilic addition to its carbonyl
group, and the enolate is a nucleophile capable of adding to a carbonyl group. And as
shown in Figure 18.4, this is exactly what happens. The product of this step is an alkox-
ide, which abstracts a proton from the solvent (usually water or ethanol) to yield a
[3-hydroxy aidehyde. A compound of this type is known as an aldol because it contains
both an aldehyde function and a hydroxyl group (ald + ol = aldol). The reaction is
called aldol addition.