Interpretation:
Reason for the preferential of nitration of pyridine at 3rd position has to be given and also resonance contributors for the intermediate formed by attack of
Explanation of Solution
Pyridine is a base, so in the presence of acid it will be protonated. For nitration at the 3rd position, the additional positive charge is delocalized on three carbon atoms of the pyridine ring. In this case, none of the resonance structures has a +2 charge on the same atom.
For nitration at the 2nd position or 4th position, the additional positive charge on the cation intermediate is also delocalized on three atoms of the pyridine ring, but one of the resonance structure has a +2 charge on nitrogen atom. This situation is less stable than that happens for nitration at the 3rd position.
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Chapter 22 Solutions
Organic Chemistry
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