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Question #45050
The Question
Consider the following multi-step reaction sequence:
- Toluene reacts with 2-chloro-2-methylpropane in the presence of anhydrous \ce{AlCl3} to form the major product \textbf{P}.
- \textbf{P} is treated with alkaline \ce{KMnO4} under vigorous heating, followed by acidification, to yield product \textbf{Q}.
- \textbf{Q} is heated with fuming \ce{H2SO4} at 373 K to give the major organic product \textbf{R}.
Identify the structure of the final major product \textbf{R}.
Options
- A.
\ce{4-tert-butyl-3-sulfobenzoic acid}
- B.
\ce{4-sulfobenzoic acid}
- C.
\ce{4-tert-butyl-2-sulfobenzoic acid}
- D.
\ce{4-tert-butylbenzenesulfonic acid}
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
Inductive Effect (I-Effect)|Electrophilic Substitution Orientation|Steric Hindrance (B-Strain)
Why This Question Is Tricky
Common Mistakes
This problem tests the limits of standard Electrophilic Aromatic Substitution (EAS) directing rules.
Students typically learn that when an activating group (+I) and a deactivating group (-I/-M) reinforce the same position, substitution occurs there exclusively (leading to Option A).
However, the 'Hidden Variable' here is extreme steric hindrance (B-strain) coupled with the leaving group ability of the tert-butyl group.
The bulky SO3 electrophile cannot access the electronically favored position 3 due to the adjacent massive tert-butyl group.
Under thermal conditions, this forces an 'ipso-substitution' where the electrophile attacks the C4 position, expelling the tert-butyl group as a stable tertiary carbocation.
Failing to account for the physical size of the reagents and the reversibility/ipso-nature of sulfonation leads directly to the trap.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2 |
| Concept | Inductive Effect (I-Effect) |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |