Arrange the following compounds in decreasing order of their acidic strength: (I) Phenol (II) p -Nitrophenol (III) m -Cresol (IV) p -Cresol

Step-by-step solution

Acidic strength of phenols depends on the stability of the phenoxide ion. Electron-withdrawing groups increase acidity, while electron-donating groups decrease acidity. In p -nitrophenol (II), the - NO ₂ group exerts strong - I and - M effects, highly stabilizing the phenoxide ion. Thus, it is the most acidic. Phenol (I) has no substituents, making it more acidic than the cresols which contain electron-donating methyl groups. In m -cresol (III), the - CH ₃ group exerts only a + I effect (hyperconjugation is absent