Question

The order of enol content in the following molecules is:

• A. a $>$ d$>$ c $>$ b
• B. a $>$ c $>$ d $>$ b
• C. a $>$ c $>$ b $>$ d
• D. a $>$ b $>$ c $>$ d

Answer 1

The correct option is A a $>$ d$>$ c $>$ b

The given keto form is converted to enol form by keto-enol tautomerism where 1,3-shift takes place.

In compound(a), the enol form contains benzene ring which implies maximum stability because of resonance.

In both compound (b) and (c), the enol forms contain same resonance effect. So, according to hyberconjugation, compound (c) is more stable than (b).

The compound (d) contains 2 keto groups which convert into 1 keto and 1 enol group, thus forming a 5-member ring. So, it is more stable than compound (c).

Order of enol content:

(a)>(d)>(c)>(b).