Nitrophenol ions, decomposition

Results of irradiation showed that photoproducts were formed as hydro-quinones, benzoquinones, and nitrophenols. Under experimental conditions, Fe3+ ion is known to promote decomposition of H202 as follows ... 

Decomposition of the substituent effect into the effect on the neutral molecule and the appropriate charged species, that is, either the conjugate acid or base, is revealing. For phenol acidity, the breakdown of the substituent effect into the two components indicates quite clearly that the interaction in the substituted phenoxide ion is the dominant one (10). In other words, p-nitrophenol is a strong acid primarily because the p-nitrophenoxide ion is relatively stable. The same is true for aniline acidity. 

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