Question

(a) Complete the mechanism for the keto-enol tautomerization below using bonds, charges, nonbonding electron pairs, and curved arrows (forward reaction only). Do not remove any pre-drawn bonds/lone pairs.(b) The tautomer that predominates in aqueous solution is the:

Answer 1

Concepts and reason

Tautomers are isomers with same carbon skeleton, but different proton and electron arrangement. Tautomers were generated by the shifting of protons from one carbon to another and exit as equilibrium mixture of two forms.

Fundamentals

Enol can undergo tautomerization to produce ketones. They always exit as the equilibrium mixture of ketone and enol form. Fine tuning of polarity of the solvent can increase the quantity of particular form.

(a)

(b)

The tautomer that predominates in aqueous solution is as follows:

Enol form is a wrong option because in the given compound enol form is less stable in an aqueous solution.

Ans: Part a

The mechanism for keto – enol tautomerization is given below.

Part b

Predominate tautomer in aqueous solution is shown below.