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Question #43999
The Question
An aqueous solution containing 1.0 equivalent of (4R, 6S)-4,6-dihydroxyheptanoic acid and 1.0 equivalent of ethanol is treated with a catalytic amount of dilute \ce{H2SO4} at 298 K. The reaction mixture is allowed to reach equilibrium without the removal of water. Which of the following is the major organic product formed?
Options
- A.
(5R)-5-((2S)-2-hydroxypropyl)oxolan-2-one
- B.
(5S)-5-((2S)-2-hydroxypropyl)oxolan-2-one
- C.
Ethyl (4R, 6S)-4,6-dihydroxyheptanoate
- D.
(5R, 7S)-5-hydroxy-7-methyloxepan-2-one
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
Nucleophilic Acyl Substitution|Esterification Reversibility|Carboxylic Acid Strength
Why This Question Is Tricky
Common Mistakes
The core trap tests the boundary between intermolecular and intramolecular thermodynamics.
Students memorize that Fischer esterification (intermolecular) fails in aqueous media because Le Chatelier's principle requires water removal to drive the equilibrium.
However, intramolecular lactonization (especially 5-membered rings) possesses a massive 'effective molarity' and favorable entropy that shifts the equilibrium strongly towards the lactone, even in water.
Secondary traps include regioselectivity (5-exo-trig vs 7-exo-trig cyclization) and stereochemical retention (the C-O bond does not break during nucleophilic acyl substitution, preventing inversion of the chiral center).
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Aldehydes, Ketones, and Carboxylic Acids - Class 12 |
| Concept | Nucleophilic Acyl Substitution |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |