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

1 Answer
Feb 11, 2018


Yes, it will show keto-enol tautomerism.


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 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.