Which of the following compounds will most readily be dehydrated to give alkene under acidic condition ?
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- 1-Pentanol
- 4-Hydroxypentan-2-one
- 3-Hydroxypentan-2-one
- 2-Hydroxycyclopentanone
The Correct Option is B
Solution and Explanation
Under acid, the ketone enolises and the protonated \(\beta\)-OH leaves, giving the conjugated enone \(\mathrm{CH_3COCH{=}CHCH_3}\) (pent-3-en-2-one), stabilised by conjugation with C=O.
1-Pentanol would need a primary carbocation (very unstable); in 3-hydroxypentan-2-one and 2-hydroxycyclopentanone the OH is on the alpha carbon, so a carbocation next to C=O is destabilised and no conjugated product forms.
Answer: (2) 4-Hydroxypentan-2-one
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