JEE AdvancedChemistryCompounds Containing NitrogenMCQ+3 / −1
In the reaction,
The structure of the product T is :
The structure of the product T is :- A

- B

- C

- D

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Correct answer: C
The problem asks for the structure of the final product T in a multi-step organic reaction starting from aniline. Let's analyze each step of the reaction sequence.
Step 1: Aniline → S
- Reactants: Aniline () and Acetic anhydride () in pyridine.
- Reaction: This is the acetylation of aniline. The amino group () is highly activating, and direct reaction with electrophiles like often leads to polysubstitution. To control the reaction, the amino group is first 'protected' by converting it into a less activating acetamido group (). The lone pair on the nitrogen of the amino group attacks one of the carbonyl carbons of acetic anhydride.
- Product S: N-phenylacetamide, also known as acetanilide (). (Aniline) (S, Acetanilide)
Step 2: S → U
- Reactants: Acetanilide (S) and Bromine () in acetic acid ().
- Reaction: This is an electrophilic aromatic substitution (bromination). The acetamido group () is an ortho, para-directing group. Because it is bulky, the para-substituted product is formed as the major product due to less steric hindrance compared to the ortho positions.
- Product U: p-bromoacetanilide. (S, Acetanilide) (U, p-bromoacetanilide)
Step 3: U → V
- Reactants: p-bromoacetanilide (U) and (acidic hydrolysis).
- Reaction: The amide group is hydrolyzed back to an amino group and a carboxylic acid. This step is the 'deprotection' of the amino group.
- Product V: p-bromoaniline. (U, p-bromoacetanilide) (V, p-bromoaniline)
Step 4: V → T
- Reactants: p-bromoaniline (V), followed by a two-step process: (1) at , and (2) .
- Reaction 1 (Diazotization): p-bromoaniline, a primary aromatic amine, reacts with nitrous acid (formed in situ from and ) at low temperatures to form a diazonium salt. (V, p-bromoaniline) (p-bromobenzenediazonium chloride)
- Reaction 2 (Deamination): The resulting diazonium salt is treated with hypophosphorous acid (). This is a reduction reaction where the diazonium group () is replaced by a hydrogen atom. This reaction is known as deamination.
- Product T: The final product is bromobenzene.
Conclusion By following the reaction sequence, the final product T is identified as bromobenzene ().
Matching with Options:
- Option A is p-bromoaniline (product V).
- Option B is p-dibromobenzene.
- Option C is bromobenzene (product T).
- Option D is benzene.
Therefore, the correct structure for product T is given in option C.
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