Product C of the following reaction sequence will be [figure]
- 1-Bromo-4-nitrobenzene
- 1, 3, 5-Tribromo-2-nitrobenzene
- 4-Bromo-1-nitrobenzene
- 1, 3, 5-Tribromobenzene
Answer
(2) 1, 3, 5-Tribromo-2-nitrobenzene
Solution
Step 1: -NH2 strongly activates the ring, so bromine water substitutes all ortho and para positions:
[figure]
A = 2,4,6-tribromoaniline (white precipitate).
Step 2: NaNO2/HCl at 273–278 K diazotises -NH2 ⇒ B = 2,4,6-tribromobenzenediazonium chloride.
Step 3: (i) HBF4 gives the diazonium fluoroborate; (ii) heating with NaNO2/Cu replaces -N2+ by -NO2:
[figure]
∴ C = 1,3,5-tribromo-2-nitrobenzene
Answer: (2)