Nitration as a double exchange reaction

At present it is generally accepted that the nitration reaction is a double exchange reaction. The nitro group becomes attached to one of the carbons in an aromatic ring, while simultaneously an atom of hydrogen initially connected with an atom of carbon, is split off as a proton  

A nitration mechanism formula of this type was suggested by Ingold [28] in 1935. 

In 1946, Dewar [29] gave the following mechanism for the double exchange with the nitracidium ion taking part  

A still more powerful brominating agent is the free Br+ ion, which is probably formed in the presence of ferric bromide used as a bromination catalyst  

By analogy it is to be expected that the N02+ is the most powerful nitrating agent. 

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Nitration as an addition reaction Nitration as a double exchange reaction... 

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