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Question #44608

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following reaction sequence:

1,2-dichloro-4-nitrobenzene $\xrightarrow[\text{65}^\circ\text{C}]{\text{NaOCH}_3 \text{ (1 equiv), CH}_3\text{OH}}$ $\text{P}$

$\text{P} \xrightarrow[\text{2. NaOH(aq)}]{\text{1. Sn, HCl, }\Delta}$ $\text{Q}$

$\text{Q} \xrightarrow[\text{2. CuCN, KCN, }\Delta]{\text{1. NaNO}_2\text{, HCl, 273 K}}$ $\text{R}$

$\text{R} \xrightarrow[\text{2. H}_3\text{O}^+\text{, }\Delta]{\text{1. CH}_3\text{MgBr (1 equiv), dry ether}}$ $\text{S}$

Identify the major product $\text{S}$ .

Options

A.
1-(3-chloro-4-methoxyphenyl)ethan-1-one
B.
1-(4-chloro-3-methoxyphenyl)ethan-1-one
C.
1-(3,4-dichlorophenyl)ethan-1-one
D.
1-(3,4-dimethoxyphenyl)ethan-1-one

Check Your Answer

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

C-X Bond Polarization and Polarizability|Nucleophilic Aromatic Substitution (SNAr)|Aryl Halide Resonance

Why This Question Is Tricky

Common Mistakes

The core trap tests the student's understanding of Nucleophilic Aromatic Substitution (SNAr) regioselectivity and the 'Aryl Halide Resonance' exception.

Students often memorize that aryl halides are unreactive due to partial double bond character (leading to Option C).

If they recognize SNAr is possible, they frequently confuse Electrophilic Aromatic Substitution (EAS) directing effects with SNAr activating effects.

In EAS, $\ce{-NO2}$ is a meta-director.

If a student incorrectly applies this to SNAr, they will substitute the meta chlorine (C2), leading to the trap Option B.

The correct logic requires identifying that SNAr is facilitated by ortho/para electron-withdrawing groups because they stabilize the negative charge in the Meisenheimer complex via resonance.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Haloalkanes and Haloarenes - Class 12
Concept	C-X Bond Polarization and Polarizability
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free