When aniline is forcefully subjected to severe extended sulfonation using concentrated sulfuric acid — Amines Chemistry Question

💡 Solution & Explanation

Sulfanilic acid contains both a strongly basic amino group ($-NH_2$) and a powerfully acidic sulfonic acid group ($-SO_3H$) within the same molecule. An internal acid-base proton transfer permanently occurs, shifting the acidic proton to the basic nitrogen, forming a highly stable, highly polar dipolar salt known as a zwitterion ($^+H_3N-C_6H_4-SO_3^-$).