Notes

Effect of Substituents on Acidic Strength in Carboxylic Acids…

The strength of carboxylic acids depends on the substituents bonded to carboxyl group.
Substituents that withdraw electron density from the acidic site tend to increase the acidity of the compound. This is because electron withdrawal stabilizes the resulting negative charge on the conjugate base, making it more favorable.
Substituents that donate electron density to the acidic site tend to decrease the acidity of the compound. This is because electron donation destabilizes the resulting negative charge on the conjugate base, making it less favorable.