Question

Phenylacetone can form two different enols.

1. Show the structures of these enols.
2. Predict which enol will be present in the larger concentration at equilibrium.

Short answer

a.

b.

Step-by-step solution

Enols

Enols constitute an intermediate that is indicated as an alkene comprising hydroxyl group connected to one side of the alkene double bond. Popular kind of the tautomerism in organic chemistry is the keto-enol tautomerism. It constitutes a chemical equilibrium existing between a keto form (ketone or aldehyde) and enol form.

Different enol forms of phenylacetone

(a)The different enol forms of phenylacetone are 1-phenylprop-1-en-2-ol and 3-phenylprop-1-en-2-ol. The different enol forms result from the different position of the double bond in the molecule. The two different enol forms of phenylacetone are given as:

Enol forms of phenylacetone

Predicting which enol will be present in the larger concentration at equilibrium

The structure which is more predominant at equilibrium is given below.

Stable enol form

The given structure is more predominant at equilibrium as it has a double bond conjugated with the benzene ring which makes it more stable than the other structure.