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NEET 2023 Phase 1 · ChemistryPrevious Year Question

Identify the product (P) in the following reaction: (the alcohol is 3-methylbutan-2-ol)

Answer: (A) (A) (2-bromo-2-methylbutane). Protonation of the and loss of water gives a secondary carbocation at C2.

  1. A.(A) (2-bromo-2-methylbutane)✓
  2. B.(B) (but-2-ene)
  3. C.(C) (2-bromo-3-methylbutane)
  4. D.(D) (1-bromo-2,2-dimethylpropane)

Correct Answer

(A) (A) (2-bromo-2-methylbutane)

Solution & Explanation

Protonation of the and loss of water gives a secondary carbocation at C2. A 1,2-hydride shift from the adjacent tertiary C-H produces the more stable tertiary carbocation, which is then captured by . The rearranged product is the tertiary bromide (2-bromo-2-methylbutane). This route with carbocation rearrangement explains why C (unrearranged) is not the major product.

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