Organic Chemistry Basics 1 Question 3
3. Which of the following compounds will show the maximum ’enol’ content?
(2019 Main, 8 April II)
(a) $\mathrm{CH}{3} \mathrm{COCH}{3}$
(b) $\mathrm{CH}{3} \mathrm{COCH}{2} \mathrm{COCH}_{3}$
(c) $\mathrm{CH}{3} \mathrm{COCH}{2} \mathrm{COOC}{2} \mathrm{H}{5}$
(d) $\mathrm{CH}{3} \mathrm{COCH}{2} \mathrm{CONH}_{2}$
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Answer:
Correct Answer: 3. (d)
Solution:
This enol-form is highly stable because of intramolecular H-bonding (6-membered stability) and due to extended conjugation.
In both of the compounds, $\mathrm{C}-2$ of $\mathrm{C}=\mathrm{O}$ group is a part of the acid derivative (ester, $-\stackrel{\mathrm{C}}{\mathrm{C}}-\mathrm{OEt}$ and acid amide, $\stackrel{|}{\mathrm{C}}-\mathrm{NH}_{2}$ ). So, $>C^{2}=0$ does not take part in enolisation, because it is already in resonance $(-R)$ with the derivative group itself.
