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Question #44040

Difficulty: 8/10 | 🟢 Free

The Question

An organic compound $\mathbf{P}$ (\ce{C8H8Cl2}) is treated with one equivalent of potassium phthalimide in DMF, followed by heating with hydrazine hydrate, to yield compound $\mathbf{Q}$ (\ce{C8H10ClN}) as the major product.

Compound $\mathbf{Q}$ gives a foul-smelling gas when heated with \ce{CHCl3} and alcoholic \ce{KOH}, but does \textbf{not} produce a red dye when treated with \ce{NaNO2}/\ce{HCl} at $0-5^\circ\text{C}$ followed by alkaline 2-naphthol. Instead, the reaction of $\mathbf{Q}$ with \ce{NaNO2}/\ce{HCl} at $0-5^\circ\text{C}$ evolves a colorless gas and forms compound $\mathbf{S}$ .

Compound $\mathbf{S}$ does \textbf{not} yield a yellow precipitate upon treatment with \ce{I2} and \ce{NaOH}. Vigorous oxidation of $\mathbf{S}$ with acidic \ce{KMnO4} yields 4-chlorobenzoic acid.

Identify the structure of $\mathbf{P}$ .

Options

A.
\ce{1-chloro-4-(2-chloroethyl)benzene}
B.
\ce{1-chloro-4-(1-chloroethyl)benzene}
C.
\ce{1,4-bis(chloromethyl)benzene}
D.
\ce{1-chloro-2-(chloromethyl)-4-methylbenzene}

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Gabriel Phthalimide Synthesis|Aniline Resonance Pitfalls

Why This Question Is Tricky

Common Mistakes

This problem tests the boundary between aliphatic and aromatic reactivity in nucleophilic substitution.

The core trap is the 'Aryl Halide Inertness' in the Gabriel Phthalimide Synthesis; students often incorrectly assume the aryl chloride can undergo $S_N2$ attack.

Furthermore, it integrates qualitative organic analysis (Carbylamine, Azo-dye, Iodoform tests) and side-chain oxidation to rigorously isolate the exact positional isomer, punishing those who ignore the negative iodoform test (differentiating primary vs secondary benzylic halides) or the exhaustive oxidation rules for alkylbenzenes.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Amines - Class 12
Concept	Gabriel Phthalimide Synthesis
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free