Chemistry - Biomolecules Question with Solution | TestHub

Sulfanilic acid (p-aminobenzenesulfonic acid) contains both an acidic group ($-S{O}_{3}H$) and a basic group ($-N{H}_2$).

The strongly acidic sulfonic acid group donates a proton to the basic amino group, resulting in the formation of an internal salt or a dipolar ion known as a zwitterion.

The structure of the zwitterion is $p{\text{-}}^{+}{H}_{3}N-C_6{H}_4-S{O}_3^{-}$.

The other given compounds do not possess a combination of a sufficiently strong acidic group and a basic group to form a stable zwitterion.

Answer: Sulfanilic acid