Which one of the following compounds, on reaction with hydrogen cyanide (HCN), gives an optically active cyanohydrin?

Step-by-step solution

Reaction of a carbonyl compound with HCN yields a cyanohydrin. For the cyanohydrin to be optically active, the carbon atom formed from the carbonyl carbon must be chiral, meaning it must be bonded to four different groups. For CH ₃ -COCH ₃ , the cyanohydrin is CH ₃ -C(OH)(CN)-CH ₃ , which has two identical methyl groups and is achiral. For H-CHO , the cyanohydrin is H-C(OH)(CN)-H , which has two identical hydrogen atoms and is achiral. For CH ₃ -CHO , the cyanohydrin is CH ₃ -CH(OH)(CN) , which has four different g