# Does "CH"_3"COCOCH"_3 show tautomerism?

Feb 11, 2018

Yes, it will show keto-enol tautomerism.

#### Explanation:

Keto-enol tautomerism

Keto-enol tautomerism is a rapid chemical equilibrium between a keto and an enol form of a carbonyl compound.

The keto form is usually the more stable, but some structural features can favour the enol.

There must be an ${\text{sp}}^{3}$ α-hydrogen next to the carbonyl carbon for tautomerism to occur.

The α-hydrogen ends up on the oxygen atom and a $\text{C=C}$ bond forms between the α-carbon and the original carbonyl carbon.

Butane-2,3-dione

Butane-2,3-dione has sp³ α-hydrogens at $\text{C-1}$ and $\text{C-4}$ that can form enols. I show only one of the enol forms below.

The keto form is almost certainly the most stable form.

I would expect little stabilization of the enol by intramolecular hydrogen bonding because the two $\text{C=O}$ bond dipoles tend to point in opposite directions.