Question

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

Answer 1

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 `"sp"^3` α-hydrogen next to the carbonyl carbon for tautomerism to occur.

The α-hydrogen ends up on the oxygen atom and a `"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 `"C-1"` and `"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 `"C=O"` bond dipoles tend to point in opposite directions.