Question

Comparing (I) and (II), which of the following statement is correct?

• A. Both (I) and (II) has similar enol content
• B. Enol content of (II) is more than (I)
• C. Enol content of (I) is more than (II)
• D. Both (I) and (II) does not exhibit Keto-enol tautomerism

Answer 1

The correct option is C Enol content of (I) is more than (II)

In Keto-enol tautomerism, delocalisation takes place between a >C=O group and an alpha H where the equilibrium lies between a keto form and an enol form.

Comparing (I) and (II), the enol form of (II) is less stable than (I) because the four membered ring has 4-$\pi$ electrons which obeys the 4n rule and thus, it becomes anti-aromatic. Since enol form of (II) is less stable than (I), the enol content of (I) will be more than (II) at equilibrium.