4-Bromopyridine N-oxide

Problem 31.16 Pyridine N-oxides not only are reactive toward electrophilic substitution, but also seem to be reactive toward nucleophilic substitution, particularly at the 2- and 4-positions. For example, treatment of 4-nitropyridine N-oxide with hydro-bromic acid gives 4-bromopyridine N-oxide. How do you account for this reactivity and orientation ... 

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