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Unformatted text preview: a resonance-stabilized cation is formed. N H H OH 2 H 2 O + N H H H N H H H N H H H In addition, protonation at the remaining carbon (C3) would also result in a less stabilized cation. Although there are two resonance structures, the remaining C=C double bond is effectively isolated, and does not confer any added stability to the cation. NH H OH 2 H 2 O + NH H H NH H H Therefore, protonation at C2 is better than either protonation at C3 or N. The two nitrogen lone pairs of imidazole are quite different. One nitrogen lone pair is part of the six- electron system and the other is not, as it lies in the s system. Accordingly, protonation occurs on the latter lone pair as aromaticity is not lost. N N H H OH 2 H 2 O + N N H H N N H H N N H . . . . =...
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