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NEET levelSingle correct optionDifficulty 1 of 3o3222

The primary bromide shown is treated with in dry acetone under the same conditions as ethyl bromide. How does its rate compare with that of ethyl bromide?

  1. AMuch faster, because primary halides always react fastest
  2. BAbout the same, because both are primary
  3. CMuch slower, because the bulky group on the beta carbon hinders backside attack
  4. DMuch faster, because a stable primary carbocation forms

Answer: C

The compound is 1-bromo-2,2-dimethylpropane (neopentyl bromide). Although primary, the bulky tert-butyl group on the beta carbon blocks the backside approach needed in , so the rate falls by several orders of magnitude relative to ethyl bromide. It is far slower.
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