Cyanohydrin Formation from Acetone

Steps:

• Identify the reactant: CH3COCH3 is acetone, a symmetrical ketone with a carbonyl group.
• Recall the reaction: Nucleophilic addition of HCN to the carbonyl forms (CH3)2C(OH)CN.
• Understand the mechanism: CN⁻ adds to the carbonyl carbon, forming a tetrahedral intermediate, followed by protonation.
• Note the requirement: HCN needs a base catalyst like KCN to generate sufficient CN⁻ nucleophile.

Why D is correct:

• Cyanide (e.g., KCN) catalyzes by providing CN⁻, which initiates nucleophilic attack on the protonated carbonyl, accelerating the reaction without being consumed.

Why the others are wrong:

• A: The product (CH3)2C(OH)CN has two identical methyl groups, so no chiral center.
• B: The reaction is nucleophilic addition of CN⁻ to the electrophilic carbonyl, not electrophilic.
• C: The intermediate contains -O⁻ and -CN after CN⁻ addition, but the statement is imprecise as no separate -CN intermediate forms before the full product.

Final answer: D