Fundamentals of Organic ChemistryChemistryAlcohols Phenols and Ethers
Identify the correct decreasing order of acidity for the following compounds: (i) (ii) (iii) (iv) (v) (vi)
Options
- Aii > iii > iv > vi > i > v
- Biii > ii > iv > vi > v > i
- Ci > ii > iii > iv > v > vi
- Dii > iii > iv > vi > v > i
Correct answer
B. iii > ii > iv > vi > v > i
Step-by-step solution
The acidity of substituted phenols depends on the stability of the conjugate base (phenoxide ion). Electron-withdrawing groups (EWG) stabilize the phenoxide ion and increase acidity, while electron-donating groups (EDG) destabilize it and decrease acidity. The electronic effects of the given para-substituents are as follows: (iii) - NO ₂ : Exhibits strong - R and - I effects. It is the strongest EWG among the given options, making p-nitrophenol the most acidic. (ii) - COCH ₃ : Exhibits - R and - I effects, but it i