Rationalise the following observations using valence-bond structures for the possible intermediates.

Pyridine undergoes electrophilic substitution only with difficulty and predominantly in the 3-position, while pyridine N-oxide undergoes electrophilic substitution very easily and predominantly at the 2- and 4-positions. (8 marks)

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E* difficult E E* + easy NF E E* difficult E E* + easy NF E

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I have drawn below all 3 possible electrophilic substitutions on pyridine If we look at second ... View the full answer