Fundamentals of Organic ChemistryChemistryAlcohols Phenols and Ethers
Arrange the following compounds in increasing order of their acidic strength: (i) Phenol (ii) m -Nitrophenol (iii) m -Chlorophenol (iv) m -Cresol
Options
- A(iv) < (i) < (iii) < (ii)
- B(iii) < (ii) < (iv) < (i)
- C(i) < (iv) < (iii) < (ii)
- D(iv) < (i) < (ii) < (iii)
Correct answer
A. (iv) < (i) < (iii) < (ii)
Step-by-step solution
Acidic strength of phenols increases with the presence of electron-withdrawing groups (EWG) and decreases with electron-donating groups (EDG). At the meta position, resonance effects do not operate, so only inductive effects influence the stability of the phenoxide ion. In m -cresol (iv), the - CH ₃ group exerts a + I effect, which destabilizes the phenoxide ion, making it less acidic than phenol (i). In m -chlorophenol (iii), the - Cl group exerts a - I effect, stabilizing the phenoxide ion and making it more acid