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Question #44392
The Question
Sodium phenoxide is treated with \ce{CO2} at 400 K and 4-7 atm pressure, followed by acid hydrolysis to yield the major product . Consider the following compounds: (I) Product (II) 3-Hydroxybenzoic acid (III) 4-Hydroxybenzoic acid (IV) Benzoic acid Identify the correct decreasing order of their acid dissociation constants () in aqueous medium at 298 K.
Options
- A.
I > II > IV > III
- B.
II > I > IV > III
- C.
IV > II > I > III
- D.
I > IV > II > III
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
Kolbe-Schmitt Reaction Mechanism|Carboxylic Acid Strength|Alpha-Hydrogen Acidity
Why This Question Is Tricky
Common Mistakes
The question tests the 'Ortho Effect' and intramolecular hydrogen bonding as exceptions to standard electronic effect predictions.
Students frequently fall into the trap of assuming the strong +M (resonance) effect of the ortho -OH group in salicylic acid will destabilize the carboxylate anion, incorrectly predicting it to be less acidic than benzoic acid or meta-hydroxybenzoic acid.
The hidden variable is the thermodynamic stabilization of the conjugate base via a 6-membered chelate ring (H-bonding), which drastically increases the of salicylic acid compared to its isomers.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Alcohols, Phenols, and Ethers - Class 12 |
| Concept | Kolbe-Schmitt Reaction Mechanism |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |