Question

Which one of the following will most readily be dehydrated in an acidic medium?
A.

B.

C.

D.

Answer 1

Hint: We have to remember that during the dehydration reaction, there occurs a conversion of reactant to the product by the loss of water. The dehydration reaction is the opposite reaction of the hydration reaction. Here, two compounds are reacted together and there is a formation of water as one product. For example, by the dehydration of alcohol there is a formation of alkene with elimination of water.

Complete answer:
The given reactant is \[4 - \]hydroxypentan\[ - 2 - \]one. And it is most readily dehydrated in acidic medium. Because, the dehydration power increases with increase the conjugation and stability of the compound. And in the case of \[4 - \]hydroxypentan\[ - 2 - \]one, the conjugation is high and the stability also very high. Therefore, in acidic medium it is most readily dehydrated and there is a formation of more stable conjugated alkene with water.
Let’s see the reaction,

Hence, option (A) is correct.
Pentan \[ - 2 - \] ol is not most readily dehydrated in the presence of acidic medium. Hence, the option (B) is incorrect.
\[3 - \] Hydroxypentan \[ - 2 - \] one is not readily reacted with acidic medium and it will not dehydrate. Hence, option (C) is incorrect.
\[5 - \] Hydroxyhexan \[ - 2 - \] one is not a stable compound and it will not readily dehydrate with acidic medium. Hence, the option (D) is incorrect.

Hence, option (A) is correct.

Note:
We need to know that the dehydration reaction mainly depends on conjugation and stability. The power dehydration reaction is directly proportional to the conjugation and stability of the compound. If the compound is more stable, it has higher conjugation. Accordingly, dehydration also increases. The dehydration of alcohol gives more conjugated alkene with the water molecules.