Question

Can 2,4-pentanedione undergo an intramolecular aldol addition? If so, why? If not, why not?

Short answer

No,2,4-pentanedione does not undergo an intramolecular aldol addition due to formation of a strained four-membered ring.

Step-by-step solution

Step-by-Step Solution Step 1: Intramolecular aldol addition  of Diketones

Diketones have two different sets of alpha-hydrogens. They can potentially form products with different membered rings, e.g., 3-membered, 4-membered, 5-membered,6-membered, etc.

The greater stability of the rings, it draws the equilibria towards its formation; therefore, the products with the more stable ring is the only product formed from the intramolecular aldol addition reactions.

Intramolecular Aldol Addition

2,4-pentanedione does not undergo an intramolecular addition reaction because if it does so it will form a strained four-membered ring of 3-hydroxy-3 -methylcyclobutanone.

Therefore 2,4-pentanedione undergoes an intermolecular reaction in which the removal of a proton from more acidic central carbon leads to the formation of a product 3-acetyl-4-hydroxy-4-methyl heptane-2,6-dione.

The formation of intermolecular product over intramolecular product is shown as follows:

Formation of intermolecular product