COMEDK2023Evening ShiftChemistryCarboxylic Acid DerivativesActual
Which one of the following correctly represents the decreasing order of acidic nature of the given carboxylic acids: [A] 2-Hydroxybenzoic acid [B] Benzoic acid [C] 3-Hydroxybenzoic acid [D] 4- Hydroxybenzoic acid
Options
- A[ A ]>[ C ]>[ B ]>[ D ]
- B[ D ]>[ C ]>[ B ]>[ A ]
- C[ D ]>[ B ]>[ C ]>[ A ]
- D[ B ]>[ A ]>[ C ]>[ D ]
Correct answer
A. [ A ]>[ C ]>[ B ]>[ D ]
Step-by-step solution
The acidity of substituted benzoic acids is determined by the electronic effects of the substituents. The -OH group exerts both an electron-withdrawing inductive effect (-I) and an electron-donating resonance effect (+M). In 2-hydroxybenzoic acid (salicylic acid), the ortho-effect and intramolecular hydrogen bonding significantly stabilize the conjugate base (carboxylate anion), making it the most acidic among the given compounds. In 3-hydroxybenzoic acid, the -OH group is at the meta position. Resonance effects do