Class 12 NEET Chemistry Alcohols, Phenols And Ethers

III > II > IV > I
Since phenols and carboxylic acids are more acidic than aliphatic alcohols, we find that cyclohexanol (I) is least acidic.
Out of the two given phenols, III is more acidic than IV. This is because of the presence of three highly electron withdrawing −NO2 groups on the benzene ring which makes the O— Hbond extremely polarized. This facilitates the release of H as H+. Thus, III > IV.
In acetic acid the electrons with drawing −

O ||

C

− in the −COOH group polarises the O— H bond and increases the acidic strength. Acetic acid is therefore more acidic than phenol or cyclohexanol.
∴ The order is III > II > IV > I.