Question

For the given compounds:


Here x, y, z represent enol content. The correct order is :

• A. x > y > z
• B. z > y > x
• C. y > x > z
• D. x > z > y

Answer 1

The correct option is D x > z > y

For (a) :


Enol form (a) is cyclic, is planar , has conjugation and $6\pi$ electrons i.e. it has $(4n+2)\pi e^{-}$ . So it is aromatic whereas (b) and (c) are not aromatic
So (a) is the most stable enol form.
Comparing (b) and (c) :

Alpha hydrogen in ketone (c) is more acidic as compared to ester (b). Also, generally esters do not show tautomerism as on removing the alpha $H$ there is cross conjugation (with lone pair of O) which destablises the enol form. So, (c) is more prone to show keto-enol tautomerism.
So % of, z > y
The order of enol content is proportional to the stability of enol compounds formed.
The correct order is :
x > z > y