What reaction occurs at the alpha-hydrogen during aldol condensation?

During aldol condensation, the reaction that occurs at the alpha-hydrogen involves deprotonation. In this process, a base abstracts a proton from the alpha-carbon of a carbonyl compound (such as an aldehyde or ketone), resulting in the formation of an enolate ion. This enolate is a reactive intermediate that can then attack another carbonyl group, leading to the formation of a β-hydroxy carbonyl compound.

Deprotonation is crucial because it creates the nucleophile (the enolate) that drives the condensation reaction forward. The reaction sequence after the formation of the enolate encompasses the nucleophilic attack on the carbonyl carbon, producing the aldol product. Further reactions, such as dehydration, may follow to yield a more stable product, but the initial step involving the alpha-hydrogen is fundamentally deprotonation.