COMEDK 2025 Morning Solved Paper

Concept:Zwitterion formation requires a strong proton donor and a sufficiently basic amine group in the same molecule.Explanation:2‑Aminoethanoic acid (glycine) has a $-\mathrm{COOH}$ group, which is a strong proton donor, and a basic $-\mathrm{NH}_{2}$ group.It undergoes intramolecular proton transfer to form the dipolar ion ${}^{-}\mathrm{OOC}-\mathrm{CH}_{2}-\mathrm{NH}_{3}^{+}$.$p$‑Aminobenzenesulphonic acid has an even stronger $-\mathrm{SO}_{3}\mathrm{H}$ group, and its $-\mathrm{NH}_{2}$ is sufficiently basic, so it also forms a zwitterion: ${}^{+}\mathrm{H}_{3}\mathrm{N}-\mathrm{C}_{6}\mathrm{H}_{4}-\mathrm{SO}_{3}^{-}$.In $p$‑aminobenzoic acid, the $-\mathrm{COOH}$ group ($pK_{a} \approx 4.2$) is not acidic enough relative to the aniline‑type $-\mathrm{NH}_{2}$ (conjugate acid $pK_{a} \approx 4.6$), and the para geometry hinders internal transfer. Hence no stable internal salt is formed.Therefore the Assertion is correct.The Reason states: “When the acid group is a relatively strong proton donor and the $-\mathrm{NH}_{2}$ group is sufficiently basic, it can accept a $\mathrm{H}^{+}$ ion from the acid group to form the dipolar ion.” This correctly explains why the first two compounds form zwitterions but the third does not.Thus both Assertion and Reason are true, and the Reason correctly explains the Assertion.Answer:Option A: Both A and R are correct and R is the correct explanation of A.