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Question #45057

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The Question

Compound $\mathbf{X}$ is 3,5-dimethylphenol. It undergoes the following sequence of reactions:

$\mathbf{X}$ is treated with 2-methylpropene in the presence of catalytic $\ce{H3PO4}$ at 298 K to yield $\mathbf{Y}$ as the major product.
$\mathbf{Y}$ is heated with Zinc dust to yield a hydrocarbon $\mathbf{Z}$ .
$\mathbf{Z}$ is subjected to vigorous oxidation using hot alkaline $\ce{KMnO4}$ followed by acidification ( $\ce{H3O+}$ ) to yield compound $\mathbf{W}$ .

Identify the correct IUPAC name of compound $\mathbf{W}$ .

Options

A.
4-\textit{tert}-butylbenzene-1,3-dicarboxylic acid
B.
2-\textit{tert}-butylbenzene-1,3-dicarboxylic acid
C.
Benzene-1,2,4-tricarboxylic acid
D.
4-\textit{tert}-butyl-5-hydroxybenzene-1,3-dicarboxylic acid

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

Hyperconjugation Logic|EAS in Phenols

Why This Question Is Tricky

Common Mistakes

The core trap tests the competition between electronic activation (hyperconjugation/+M) and steric hindrance in Electrophilic Aromatic Substitution (EAS).

Students often assume that the position with maximum electronic stabilization dictates the major product.

In 3,5-dimethylphenol, the C4 position is \textit{para} to the strongly activating -OH group and receives hyperconjugative electron density from two adjacent methyl groups, making it electronically superior.

However, the hidden variable is the massive steric bulk of the \textit{tert}-butyl electrophile.

The C4 position is flanked by two methyl groups, creating an impenetrable steric shield.

The reaction is forced to redirect to the C2 position, which is flanked by a much smaller hydroxyl group.

Further steps test the knowledge of phenol reduction via Zn dust and the fact that \textit{tert}-butyl groups resist benzylic oxidation due to the absence of $\alpha$ -hydrogens.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2
Concept	Hyperconjugation Logic
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free