Question

Why is 2,4 pentanedione more highly enolized than 1,3 cyclohexanedione?

Answer 1

Enolization of acetylacetone allows a 6-membered ring, stabilized by hydrogen bonding.

Explanation:

On the other hand, when the cyclic dione enolizes, because the oxygen centres are constrained by the ring, and hydrogen bonding would occur intermolecularly, rather than intramolecularly.

I am trying to think how you would be able to test this hypothesis. Maybe the `pK_a` of each dione would be revealing.