Question

When propionaldehyde is warmed with sodium hydroxide, one of the products is 2-methylpent-2-enal. Propose a mechanism for this reaction.

Short answer

Base-catalyzed aldol condensation reactionfollows thenucleophilic addition reaction.

In this reaction,enolate is formed, which acts as the strong nucleophile, thus getting attached carbon (electrophile)of the carbonyl group.

Step-by-step solution

Base-catalyzed Aldol condensation

Base-catalyzed aldol condensation reactionfollows thenucleophilic addition reaction.

In this reaction,enolate is formed, which acts as the strong nucleophile, thus getting attached carbon (electrophile)of the carbonyl group.

Mechanism for propionaldehyde when reacted with sodium hydroxide

When reacted with sodium hydroxide, propionaldehyde follows the base-catalyzed aldol condensation mechanism in which sodium hydroxide (base) removes a proton to form an enolate ion. The formed enolate ion adds to the carbonyl group of another propionaldehyde molecule. In the last step, Protonation of the alkoxide gives the aldol product 2-methylpent-2-enal.