A) \[I>II>III\]
B) \[III>II>I\]
C) \[II>I>III\]
D) \[II>III>I\]
Correct Answer: B
Solution :
The rolls of \[\text{ }\!\!\beta\!\!\text{ -}\]dicarbonyl compounds are more stable because of conjugation and intermolecular H-bonding. Thus, the order of stability is \[\underset{\text{III}}{\mathop{\underset{\begin{smallmatrix} \text{(Stabilised}\,\text{by}\,\text{conjugation} \\ \text{and}\,\text{H-bonding)} \end{smallmatrix}}{\mathop{{{\text{H}}_{\text{3}}}\text{C}-\overset{\begin{smallmatrix} \text{OH} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,\text{=}\,\text{CH}-\overset{\begin{smallmatrix} \text{O} \\ \text{ }\!\!|\!\!\text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,-\text{C}{{\text{H}}_{\text{3}}}}}\,}}\,\]\[\text{}\,\text{C}{{\text{H}}_{\text{3}}}-\overset{\begin{smallmatrix} \text{O} \\ \text{ }\!\!|\!\!\text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,-\underset{\text{II}}{\mathop{\text{C}{{\text{H}}_{\text{2}}}}}\,-\overset{\begin{smallmatrix} \text{O} \\ \text{ }\!\!|\!\!\text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,-\text{C}{{\text{H}}_{\text{3}}}\]\[\underset{\text{I}}{\mathop{\underset{\begin{smallmatrix} \text{Less}\,\text{Stable}\,\text{as}\,\text{(=)bond} \\ \text{is}\,\text{not}\,\text{in}\,\text{conjugation}\,\text{with}\,\text{carbonyl}\,\text{group} \end{smallmatrix}}{\mathop{\text{}\,\text{C}{{\text{H}}_{\text{3}}}=\overset{\begin{smallmatrix} \text{O} \\ \text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,-\text{C}{{\text{H}}_{\text{2}}}-\overset{\begin{smallmatrix} \text{O} \\ \text{ }\!\!|\!\!\text{ }\!\!|\!\!\text{ } \end{smallmatrix}}{\mathop{\text{C}}}\,-\text{C}{{\text{H}}_{\text{3}}}}}\,}}\,\]
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