The major product (A) formed in the following reaction sequence is [figure]
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- [figure]
- [figure]
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Answer
(2) [figure]
Solution
(i) Sn/HCl reduces -NO2 to -NH2 (aniline).
(ii) Ac2O/pyridine acetylates it to acetanilide; the lone pair on N is now also in resonance with C=O, so -NHCOCH3 is only a moderately activating o/p-director.
(iii) Br2/AcOH gives mainly the para-bromo product (ortho is hindered by the bulky group).
(iv) aqueous NaOH hydrolyses the amide back to the free amine.
[figure]
A is 4-bromoaniline.
Answer: (2)