Nucleophilic Substitution Reaction

Steps:

• Identify reactants: CH₃I is an alkyl halide; NH₃ is a nucleophile.
• Observe products: CH₃NH₂ shows I replaced by NH₂ group.
• Recognize pattern: Nucleophile (NH₃) attacks electrophilic carbon, displacing leaving group (I⁻).
• Classify mechanism: SN2 substitution for primary alkyl halide like CH₃I.

Why D is correct:

• Nucleophilic substitution defined as nucleophile replacing leaving group on carbon (here, NH₃ attacks C, I⁻ leaves).

Why the others are wrong:

• A: Electrophilic addition involves pi bonds (e.g., alkenes), absent here.
• B: Free-radical substitution requires radical initiation (e.g., UV light), not present.
• C: Nucleophilic addition targets unsaturated bonds (e.g., carbonyls), not saturated C-I.

Final answer: D