NEET 2023 Phase 1 · ChemistrySandmeyerPrevious Year Question
Identify the final product in the following reaction sequence:
Answer: (B) (B) Benzene, . \textbf{Answer:} (B) Bromobenzene phenylmagnesium bromide benzene on hydrolysis.
- A.(A) Phenol,
- B.(B) Benzene, ✓
- C.(C) Phenylmagnesium bromide,
- D.(D) 4-Bromophenol,
Correct Answer
(B) (B) Benzene,
Solution & Explanation
\textbf{Answer:} (B) Bromobenzene phenylmagnesium bromide benzene on hydrolysis. \textbf{Solution:} Step (i): Gattermann/Sandmeyer-type replacement of the diazonium group by bromine using cuprous bromide: (bromobenzene), with loss of . Step (ii): bromobenzene with in dry ether forms the Grignard reagent phenylmagnesium bromide: . Step (iii): a Grignard reagent reacts with water (a source of acidic ) and is protonated to the parent hydrocarbon: . The final product is therefore benzene (B). (C) is only the intermediate before hydrolysis; phenol and 4-bromophenol do not arise from this route.
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