MolSynapsequestion bank
MolSynapse / Question bank / Organic Reaction Mechanisms III: Nucleophilic Substitution / SN1 vs SN2 preference and rate order for drawn substrates
NEET levelSingle correct optionDifficulty 1 of 3o3221

The tertiary bromide shown is warmed in aqueous ethanol with no added base or other nucleophile. Which mechanism operates for the substitution?

  1. A, with water attacking from the back side
  2. B, because water is a strong nucleophile
  3. CNo substitution, because tertiary halides are inert
  4. D, through a tertiary carbocation

Answer: D

The compound is 2-bromo-2-methylpropane. A tertiary halide in a polar protic solvent with only a weak nucleophile ionises slowly to a tertiary carbocation (rate = ), which the solvent then captures. Backside attack at a tertiary carbon is blocked, so does not compete. The mechanism is .
Practice Organic Reaction Mechanisms III: Nucleophilic Substitution More on SN1 vs SN2 preference and rate order for drawn substrates
Previous questionNext question

More questions on SN1 vs SN2 preference and rate order for drawn substrates