Question

Which of the following structure contain a hemiacetal group?

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

Aldehydes react with one equivalent of monohydric alcohol in the presence of dry hydrogen chloride to yield alkoxyalcohol intermediate, known as hemiacetals which further reacts with one more molecule of alcohol to give a $\text{gem-dialkoxy}$ known as $\text{acetal.}$

$C$ atom has $-OH$ group, $-OR$ group & $-H$ atoms
so, it is hemiacetal.
a and c are hemiketal.
d is acetal.
Hence answer is option (b).