Chemistry - GOC Question with Solution | TestHub

In (a) the OH is para, where it donates electron density by resonance toward the COOH group, destabilising the carboxylate : (a) is even weaker than benzoic acid (pKa ≈ 4.6). In (b) (salicylic acid) the ortho OH forms a strong intramolecular hydrogen bond with the carboxylate, stabilising it (pKa 2.97). In (c) both ortho positions carry OH groups, so the anion is chelated on both sides and stabilised the most (pKa ≈ 1.3). Hence (a) $<$ (b) $<$ (c).