Can the electrophile attack at the position of the NH2 group in nitration of aniline?

In the nitration of aniline, we observe the formation of a meta-substituted product (47%) almost as much as a para (52%).


However, can't the electrophile attack at the position where $\ce{-NH2}$ is already attached, so that after the attack, it will be stabilised by the mesomeric (+) effect of $\ce{-NH2}$? Maybe just after some time, the $\ce{-NH2}$ group will become $\ce{-NH3+}$ (acidic medium) and $\ce{NH3}$ would depart as a leaving group?





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> Maybe just after some time, the $\ce{-NH2}$ group will become $\ce{−NH3+}$ (acidic medium) and $\ce{NH3}$ would depart as a leaving group?
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No! You are confusing the leaving group oxonium ion with the ammonium ion. Simply put it, $\ce{R-NH2}$ does **not** leave as $\ce{R+}$ and $\ce{NH3}$, as you might expect from the hydroxyl group leaving mechanism.


But that does not mean there is no other way to make an $\ce{-NH2}$ group (which is a very bad leaving group) leave. You can instead make it leave as dinitrogen gas!


The way this works is by the reaction of $\ce{R-NH2}$ with $\ce{HNO2}$. If $\ce{R}$ is an:


* **aromatic group**: a diazonium ion, $\ce{R-N2+}$, will be formed (stable at ice cold temperature). Further reactions such as Balz-Schiemann, Gattermann, Sandmeyer, etc. may be employed to replace the $\ce{-N2+}$ with another group, and make it leave as dinitrogen gas.
* **alkyl group**: $\ce{R-N2+}$ will be formed but it will, being highly unstable (given that it does not enjoy the resonance stabilization of an aromatic ring), instantly decompose to release dinitrogen gas and form a classical carbocation $\ce{R+}$. This carbocation may rearrange, if necessary, and then receive an attack by a nucleophile.


This is how you make the bad leaving group, $\ce{-NH2}$, leave any aromatic ring or an alkyl group. 


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With nitric acid as a nitrating agent, the difficulty is that the acid protonates the amino group and destroys its nucleophility.


However, other compounds may provide a nitryl ion moiety without a protic hydrogen, thus leaving the nitrogen open to nitration. A casual Google search does not turn up an example with aniline, but [ammonia can be converted to nitramide at nitrogen by $\ce{N2O5}$:](https://en.wikipedia.org/wiki/Nitramide)


$\ce{N2O5 + 2NH3 -> \underset{nitramide}{H2NNO2} + NH4NO3}$


The $\ce{NO2^+}$ portion of the $\ce{N2O5}$ nitrates a nitrogen atom on the ammonia molecule, and the displaced proton is scooped up by a second ammonia molecule to form a salt (ammonium nitrate) with the $\ce{NO3^-}$ part of the original nitrogen pentoxide.


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