Chapter 18, Problem 1PP

Interpretation Introduction

Interpretation: The structures of cyclohexa-2, 4-dien-1-one and its enol form are to be written, and the special factors that account for the stability of the enol form are to be identified.

Concept introduction:

Tautomerization is defined as the interconversion of the keto and enol forms. The keto and enol forms are tautomers.

The conjugate base of both the keto and the enol forms is enolate.

If the enolate accepts a proton from carbon, the keto form is formed, and if the enolate accepts a proton from oxygen, the enol form is formed.

Answer to Problem 1PP

Solution:

Due to aromaticity.

Explanation of Solution

Under acidic condition, cyclohexa-2, 4-dien-1-one converts to phenol through tautomerism. The structures of cyclohexa-2, 4-dien-1-one and its enol form are as follows:

Ketones are usually more stable than enols. However, in this case, the enol form is more stable because the enol form is phenol, which is aromatic in nature, whereas, in the keto form, there is no aromatic character. Hence, due to its aromaticity, the enol form is more stable.