AIIMS 2019 Chemistry Effect of Substituents MCQ Question

Option B is correct because compound (b) exhibits intermolecular hydrogen bonding, which stabilizes its structure and reduces its acidity compared to compound (a), where the -NO₂ group exerts a strong -M effect, enhancing acidity. In contrast, compound (c) has a methyl group, which is an electron-donating group that decreases acidity by destabilizing the conjugate base, while compound (d) lacks such a group, making it more acidic than (c) but less than (b) due to the absence of hydrogen bonding. Thus, the order of acidity is influenced by the presence of electron-withdrawing or donating groups and hydrogen bonding interactions.