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Question #45063

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The Question

Consider 2,6-di-tert-butylphenol (Compound \textbf{X}).

Reaction 1: \textbf{X} is treated with \ce{Br2} in \ce{CS2} at 273 K to yield a mono-brominated major product \textbf{Y}.

Reaction 2: \textbf{X} is subjected to O-acetylation under forcing conditions to form Compound \textbf{Z} (2,6-di-tert-butylphenyl acetate).

Reaction 3: \textbf{Z} is treated with \ce{Br2} and \ce{FeBr3} at 298 K to yield a mono-brominated major product \textbf{W}.

Identify the positions of the newly introduced bromine atoms in the aromatic rings of \textbf{Y} and \textbf{W} respectively. (Assume the oxygen-bearing carbon is designated as C-1).

Options

A.
\textbf{Y}: C-4 ; \textbf{W}: C-4
B.
\textbf{Y}: C-4 ; \textbf{W}: C-3
C.
\textbf{Y}: C-3 ; \textbf{W}: C-4
D.
\textbf{Y}: C-3 ; \textbf{W}: C-3

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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

Electromeric Effect|EAS in Phenols|Esterification Steric Hindrance

Why This Question Is Tricky

Common Mistakes

This question tests the concept of Steric Inhibition of Resonance (SIR) and its profound effect on regioselectivity in Electrophilic Aromatic Substitution.

Students often blindly apply the rule that oxygen-containing substituents (\ce{-OH}, \ce{-OAc}) are always ortho/para directing due to their $+M$ effect.

However, when flanked by bulky ortho-substituents (like tert-butyl groups), the larger \ce{-OAc} group is forced out of coplanarity with the ring, completely shutting down its $+M$ effect.

It then acts purely as an electron-withdrawing group via its $-I$ effect, switching its directing nature from ortho/para to meta.

The smaller \ce{-OH} group in the precursor avoids this steric clash, retaining its $+M$ effect and para-directing nature.

Quick Facts About This Question

Question Information

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