The phenylhydroxylamine rearrangement

Phenylhydroxylamine (LV) is converted in 2 N aqueous sulphuric acid at room temperature to pura-aminophenol (LVI), viz. 

Yukawa98 has written a reaction scheme involving reaction via LIX, but this mechanism does not account so readily for the products. 

N-substituted phenylhydroxylamine derivatives, e.g. N-acetyl and N-sulphonic acid, also form the para-aminophenol , but more bulky groups prevent reaction, it is thought by steric hindrance to the approach of the hydronium ion. -substituted phenylhydroxylamines, on the other hand form only the ortho product, it is thought via an intramolecular rearrangement, e.g. 

This reaction has been shown100 to be involved in the degradation in vivo of carcinogenic arylamines by N-hydroxylation and subsequent rearrangement. 

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