Question

Which of the following compounds is hemiacetal?
A)
B)
C)
D) All of these

Answer 1

To answer this question, you must recall the characteristics of a hemiacetal group. A hemiacetal is a compound which contains a carbon atom attached to a hydroxyl group on one side and to ether on the other. Checking all the options for the hemiacetal group, we would get our answer.

Complete step by step solution:
Hemiacetals are obtained as a result of the addition of an alcohol to a ketone. A hemiacetal group can be represented as
$HC\left( {OH} \right)\left( {OR} \right)R'$
In option A, we can observe that the carbon atom has a hydroxyl group at one end and with ether on the other end. Thus, it is a hemiacetal.
In option B, we can observe that the carbon atom is attached to a hydroxyl group at one end and to ether on the other end. Thus, it is a hemiacetal as well.
In option C, we can observe that the carbon atom is attached to a hydroxyl group at one end and toan ether on the other end. Thus, it is a hemiacetal as well.
So, we can conclude by saying that all the given compounds are hemiacetals.

Hence, the correct option is D.

Note:
Acetal group and hemiacetal group are very similar in both their names as well as their structures. Acetal group contains a carbon atom bonded to two ether groups at the same time and is thus very similar to the hemiacetal group in which the carbon atom is attached to an ether group and a hydroxyl group. On reaction with oxidizing agents, they give aldehyde and alcohol.