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NEET 2023 Phase 2 · ChemistrySandmeyerPrevious Year Question

Choose the correct sequence of reagents in the conversion of 4-nitrotoluene to 2-bromotoluene.

Answer: (A) (A) ; ; ; . \textbf{Answer:} (A) Brominate first (directed by the / positions to the required carbon), then reduce, diazotise, and finally remove the diazonium group by deamination.

  1. A.(A) ; ; ; ✓
  2. B.(B) ; ; ;
  3. C.(C) ; ; ;
  4. D.(D) ; ; ;

Correct Answer

(A) (A) ; ; ;

Solution & Explanation

\textbf{Answer:} (A) Brominate first (directed by the / positions to the required carbon), then reduce, diazotise, and finally remove the diazonium group by deamination. \textbf{Solution:} Target: place at the position ortho to (the carbon that originally bears ), so that after removing the nitrogen function we are left with \textbf{2-bromotoluene} (-bromotoluene). Step 1 \textbf{Bromination} of 4-nitrotoluene with introduces ortho to the methyl group (meta to the ), giving 2-bromo-4-nitrotoluene: Step 2 \textbf{Reduction} of the nitro group to an amino group with : (2-bromo-4-methylaniline). Step 3 \textbf{Diazotisation} of the with at 273278 K gives the arenediazonium salt: Step 4 \textbf{Deamination} (reductive removal of ) with hypophosphorous acid in water replaces by : leaving 2-bromotoluene. The sequence ; ; ; corresponds to option (A).

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