JEE Chemistry Question

Given: A reaction sequence starting from benzene leads to product T. The task is to find the percentage of nitrogen in T. Find: Percentage of nitrogen in product T, nearest integer. From the solution sequence: 1. Benzene on nitration gives nitrobenzene. 2. Reduction gives aniline. 3. Acetylation gives acetanilide. 4. Nitration of acetanilide gives mainly p-nitroacetanilide because the -NHCOCH3 group is ortho/para directing and the para product is major. 5. Hydrolysis regenerates the amine group, so product T is p-nitroaniline. For p-nitroaniline, the molecular formula is C6H6N2O2 Therefore, its molar mass is 6(12) + 6(1) + 2(14) + 2(16) = 72 + 6 + 28 + 32 = 138 g/mol Total mass of nitrogen in one mole is 2 14 = 28 g Now calculate percentage of nitrogen: N = 28138 100 N 20.28 Nearest integer: 20 Therefore, the required numerical answer is 20. The provided correct answer field shows 21, but the solution working clearly gives 20.28, so the nearest integer is 20.

JEE Question — Solution | JEE Chemistry

NVAMediumJEE 2026Electrophilic Substitution in Benzene

Reaction sequence starting from benzene through nitration, reduction, acetylation, further nitration and hydrolysis to product T, asking percentage of nitrogen in T with atomic masses H 1, C 12, N 14, O 16.

Answer

Correct answer:20

Step-by-step solution

Standard Method

Given: A reaction sequence starting from benzene leads to product T. The task is to find the percentage of nitrogen in T.

Find: Percentage of nitrogen in product T, nearest integer.

From the solution sequence:

Benzene on nitration gives nitrobenzene.
Reduction gives aniline.
Acetylation gives acetanilide.
Nitration of acetanilide gives mainly p-nitroacetanilide because the $-NHCOCH_3$ group is ortho/para directing and the para product is major.
Hydrolysis regenerates the amine group, so product T is p-nitroaniline.

For p-nitroaniline, the molecular formula is

C_6H_6N_2O_2

Therefore, its molar mass is

6(12) + 6(1) + 2(14) + 2(16) = 72 + 6 + 28 + 32 = 138 \, \text{g/mol}

Total mass of nitrogen in one mole is

2 \times 14 = 28 \, \text{g}

Detailed Calculation

Now calculate percentage of nitrogen:

\%N = \frac{28}{138} \times 100

\%N \approx 20.28\%

Nearest integer:

20

Therefore, the required numerical answer is 20.

The provided correct answer field shows 21, but the solution working clearly gives $20.28\%$ , so the nearest integer is 20.

Common mistakes

Identifying T incorrectly as acetanilide or p-nitroacetanilide is wrong because the final hydrolysis step removes the acetyl protecting group. Always track the last reaction before calculating the formula.
Using the wrong molecular formula for p-nitroaniline leads to an incorrect percentage. After hydrolysis, the correct formula is $C_6H_6N_2O_2$ , not the acetylated intermediate.
Rounding $20.28$ to $21$ is incorrect because the nearest integer to $20.28$ is $20$ . Round only after completing the full calculation.

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