Reaction of nitrobenzene with potassium ferricyanide

I came across this question in an exercise book. Can anyone give detailed answer (mechanism) of this reaction?
  

[![enter image description here](https://i.stack.imgur.com/cxMZj.png)](https://i.stack.imgur.com/cxMZj.png)


I am unable to proceed. I thought there maybe some redox reaction involved where $$\ce{Fe^3+ -> Fe^2+}$$ maybe taking place but then nitrobenzene would have to be oxidised. Can someone please help ?




I'd go more for an oxidation, but on the ring (hydroxylation). 
My guess comes from this paper here : ["The Hydroxylation of Aromatic Nitro Compounds by Alkalies" by O. C. Dermer](http://ojs.library.okstate.edu/osu/index.php/OAS/article/view/5955/5577).


This is very harsh (and somehow old) chemistry. 


First, for *m*-dinitrobenzene and *sym*-trinitrobenzene, hydroxylation is reported in your conditions, that is to say alcaline conditions with the help of potassium ferricyanide as oxidizing agent (reactions A and B, see reference in the paper). 


Second, the authors report the reaction C (with less than 4% yield though, according to my calculations), with a small amount of *p*-hydroxyazobenzene as a side-product. They did this reaction by mixing only nitrobenzene with potassium hydroxide, so I would expect the same product (*o*-nitrophenol) with maybe a better yield in your conditions.


[![enter image description here](https://i.stack.imgur.com/dzxjH.png)](https://i.stack.imgur.com/dzxjH.png)


 3

First, since there are no electrophiles that are formed, the only reaction that comes to mind is nucleophilic aromatic substitution.


$\ce{NaOH}$ does a displacement reaction with $\ce{K3Fe(CN)6}$, yielding the $\ce{CN-}$ ion.


The cyanide ion attacks the benzene ring, giving three possible resonance structures:


[![enter image description here](https://i.stack.imgur.com/j6N7H.png)](https://i.stack.imgur.com/j6N7H.png)


The hydrogen attached to the carbon with the cyanide ion is accepted by the strong base $\ce{NaOH}$.


Next, the nitrile undergoes acid-catalysed hydrolysis to form a carboxylic acid:


[![enter image description here](https://i.stack.imgur.com/Yo9Yu.png)](https://i.stack.imgur.com/Yo9Yu.png)


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