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Question #43988
The Question
Consider two separate equimolar mixtures at 298 K: Mixture I: 2-Methylbenzoic acid and 4-Methylbenzoic acid. Mixture II: 2-Methylaniline and 4-Methylaniline.
Experiment 1: Mixture I is treated with 1.0 equivalent of aqueous \ce{NaOH}. The resulting solution is washed with ether, and the aqueous layer is subsequently acidified to yield predominantly compound . Experiment 2: Mixture II is treated with 1.0 equivalent of benzenesulfonyl chloride (\ce{PhSO2Cl}) in the presence of excess pyridine. The major sulfonamide product formed is .
Identify and , along with the primary structural phenomenon governing their predominant formation.
Options
- A.
: 2-Methylbenzoic acid (SIR effect); : N-(4-Methylphenyl)benzenesulfonamide (Steric hindrance)
- B.
: 4-Methylbenzoic acid (+I effect); : N-(2-Methylphenyl)benzenesulfonamide (SIR effect)
- C.
: 2-Methylbenzoic acid (SIR effect); : N-(2-Methylphenyl)benzenesulfonamide (Ortho-effect)
- D.
: 4-Methylbenzoic acid (Steric hindrance); : N-(4-Methylphenyl)benzenesulfonamide (+I effect)
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
Carboxylic Acid Strength|Hinsberg Reagent Selectivity|Ortho-Effect in Anilines
Why This Question Is Tricky
Common Mistakes
The problem tests the dual and often contradictory nature of the 'Ortho-Effect' in aromatic systems.
Students frequently memorize that the ortho-effect 'increases reactivity' or blindly apply Steric Inhibition of Resonance (SIR) to all functional groups.
While SIR forces the carboxylate group out of plane (increasing acidity by preventing cross-conjugation), primary amines (\ce{-NH2}) are small enough that SIR is negligible.
Instead, the ortho-substituent in anilines primarily causes steric hindrance to solvation and electrophilic attack, thereby decreasing basicity and nucleophilicity.
The trap lies in assuming the ortho-effect enhances nucleophilicity in anilines just as it enhances acidity in benzoic acids, which would incorrectly lead to selecting 2-methylaniline as the precursor for .
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Aldehydes, Ketones, and Carboxylic Acids - Class 12 |
| Concept | Carboxylic Acid Strength |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |