Why does a tertiary alkyl halide mainly react with a weak nucleophile by an SN1 mechanism?
Answer and explanation
Correct answer: A. It forms a stable tertiary carbocation, and bulky groups block backside attack
- Step 1: Three alkyl groups stabilise a carbocation by induction and hyperconjugation. Step 2. The same groups crowd the carbon, so SN2 attack from behind is hindered. Answer: stable carbocation and steric hindrance. Why not the others: primary cations are unstable, a concerted two-reactant rate law describes SN2, and radical chains need light or initiators.
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