JEE Advanced levelSingle correct optionDifficulty 3 of 3g1156
In 1H-imidazole (a five-membered ring with two nitrogen atoms at positions 1 and 3, N1 bearing hydrogen), protonation occurs on
AN1, the nitrogen bearing hydrogen
Bcarbon 2
CN3, the nitrogen without hydrogen, whose lone pair is in the ring plane
Dboth nitrogens equally in the neutral ring
Answer: C
N1 is like the pyrrole nitrogen: its lone pair is part of the 6 pi electron sextet. N3 is like the pyridine nitrogen: its lone pair is in the sp2 plane and available for protonation, without disturbing aromaticity.