What is the product formed when ${\text{CH}}_3{\text{COCH}}_3$ reacts with $\text{HCN}$?

Solution

1. The cyanide ion ${\text{CN}}^{-}$ acts as a nucleophile attacking the carbonyl carbon.
2. The oxygen atom is protonated to form a hydroxyl group.
3. The reaction of ${\text{CH}}_3{\text{COCH}}_3$ with $\text{HCN}$ yields ${\text{CH}}_3\text{C}(\text{OH})(\text{CN}){\text{CH}}_3$.
4. Hence the answer is (B).