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Question #44917

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following multi-step synthesis:

$\text{4-Nitrotoluene} \xrightarrow{Br_2, Fe} \text{P}$

$\text{P} \xrightarrow{Sn, HCl} \xrightarrow{NaOH(aq)} \text{Q}$

$\text{Q} \xrightarrow{NaNO_2, \text{dil. } HCl, H_2O, 298\text{ K}} \text{R}$

$\text{R} \xrightarrow{CHCl_3, aq. NaOH, 343\text{ K}} \xrightarrow{H_3O^+} \text{S (Major Product)}$

Identify the major product \textbf{S}.

Options

A.
4-bromo-2-hydroxy-5-methylbenzaldehyde
B.
3-bromo-2-hydroxy-4-methylbenzaldehyde
C.
3-bromo-2-hydroxy-5-methylbenzaldehyde
D.
2-bromo-4-chloro-1-methylbenzene

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Electrophilic Substitution Control|Sandmeyer vs Gattermann|Diazotization Temperature Sensitivity

Why This Question Is Tricky

Common Mistakes

The core trap lies in the temperature dependence of the diazotization reaction.

Students frequently memorize $NaNO_2/HCl$ as a generic 'diazonium generator' and blindly proceed to assume a Sandmeyer-like substitution pathway (leading to Distractor D), ignoring that at 298 K, the diazonium ion rapidly decomposes via an $S_N1$ mechanism to yield a phenol.

Additionally, the problem tests synergistic directing effects in the initial bromination (Distractor C tests the wrong EAS regioselectivity) and the steric control of regioselectivity in the Reimer-Tiemann reaction (Distractor B tests attack at the sterically hindered ortho position), forcing the student to carefully track the 3D spatial arrangement of substituents throughout the entire synthesis.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Amines - Class 12
Concept	Electrophilic Substitution Control
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free