Aniline reacts with mixed acid (conc. $\mathrm{HNO}_{3}$ and conc. $\mathrm{H}_{2}\mathrm{SO}_{4}$) at 288 K to give **P** (51%), **Q** (47%) and **R** (2%). The major product(s) of the following reaction sequence is (are) $$\mathbf{R} \xrightarrow{\ \text{steps 1) to 5)}\ } \mathbf{S} \xrightarrow{\ \text{steps 1) to 4)}\ } \text{major product(s)}$$ **R** $\rightarrow$ **S**: 1) $\mathrm{Ac}_{2}\mathrm{O}$, pyridine 2) $\mathrm{Br}_{2}$, $\mathrm{CH}_{3}\mathrm{CO}_{2}\mathrm{H}$ 3) $\mathrm{H}_{3}\mathrm{O}^{+}$ 4) $\mathrm{NaNO}_{2}$, HCl / 273-278 K 5) EtOH, $\Delta$ **S** $\rightarrow$ major product(s): 1) Sn / HCl 2) $\mathrm{Br}_{2}/\mathrm{H}_{2}\mathrm{O}$ (excess) 3) $\mathrm{NaNO}_{2}$, HCl / 273-278 K 4) $\mathrm{H}_{3}\mathrm{PO}_{2}$

Compounds Containing Nitrogen — JEE Advanced · 2018 · 20 May 2018 · Paper 2 Question with Solution

Aniline reacts with mixed acid (conc.

HNO_{3}

and conc.

H_{2} SO_{4}

) at 288 K to give P (51%), Q (47%) and R (2%). The major product(s) of the following reaction sequence is (are)

R steps 1) to 5) S steps 1) to 4) major product(s)

\to

S:
1)

Ac_{2} O

, pyridine
2)

Br_{2}

CH_{3} CO_{2} H

H_{3} O^{+}

NaNO_{2}

, HCl / 273-278 K
5) EtOH,

Δ

\to

major product(s):
1) Sn / HCl
2)

Br_{2} / H_{2} O

(excess)
3)

NaNO_{2}

, HCl / 273-278 K
4)

H_{3} PO_{2}

(A)(see structure)
(B)(see structure)
(C)(see structure)
(D)(see structure)
✓ Correct

Answer: (D)

Solution

Aniline reacts with mixed acid to give m-nitroaniline (P, 51%), p-nitroaniline (Q, 47%), and o-nitroaniline (R, 2%). The reaction sequence involves: (1) acetylation to protect the amino group, (2) bromination at ortho positions, (3) deprotection, (4) diazotization, (5) reduction to remove the diazo group. The major product P (m-nitroaniline) undergoes this sequence. After Sn/HCl reduction of the nitro group to amino, bromination in excess

Br_{2} / H_{2} O

gives tribromination at positions 2, 4, and 6. Diazotization followed by

H_{3} PO_{2}

removes the amino group, giving 1,3,5-tribromobenzene (option D).

JEE Advanced · 2018 · 20 May 2018 · Paper 2 · One or more correct options

JEE Advanced · 2018 · 20 May 2018 · Paper 2 · Compounds Containing Nitrogen

Solution

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