Question

Compound A undergoes formation of cyanohydrin which on hydrolysis gives lactic acid $(C{H}_{3}CHOHCOOH)$ . Therefore, compound A is

• A. formaldehyde
• B. acetaldehyde
• C. acetone
• D. benzaldehyde

Answer 1

Answer: (B)

Since, compound $A$ gives cyanohydrin, it must contain a carbonyl compound. Thus, its general formula should be
The other attached group to the carbon in the product (ie, lactic acid) are $C{H}_3$ and $H$. On attaching these groups, we get
This is the formula of compound $A$. Thus, compound $A$ is acetaldehyde.