Notes

Effect of Substituents on Carbolic Acid…

Effect of Substituents on Carbolic Acid, the presence of electron withdrawing groups like -NO2, -CN etc. on the benzene ring stabilises the phenoxide ion by the dispersal of negative charge, thereby, increasing the acidic strength of carbolic acid.
Whereas, presence of electron donating groups like -CH3 etc. on the benzene ring destabilises the phenoxide ion by increasing the negative charge, thereby, decreasing the acidic strength of carbolic acid.