What is the mechanism of nucleophilic substitution in tertiary alkyl halides like tert-Butyl bromide?
Answer and explanation
Correct answer: A. S_N1 mechanism
- Step 1: Tertiary alkyl halides are sterically hindered from backside attack, preventing bimolecular S_N2 mechanism. Step 2. Ionization readily forms a highly stable tertiary carbocation in the rate-determining step, which is then rapidly attacked by the nucleophile (S_N1 mechanism). Answer: S_N1 (two-step, carbocation intermediate). Why not the others: S_N2 occurs in primary alkyl halides with inversion; E2 requires strong base and heat; free radical requires light/peroxides.
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