# Question #b39a6

Dec 30, 2014

The ammonium ion, ${\text{NH}}_{4}^{+}$, can act as an electrophile.

#### Explanation:

An electrophile is a species that accepts a pair of electrons to form a new covalent bond.

This should sound familiar. It is the definition of a Lewis acid!

In the reaction $\text{NH"_4^+ + "OH"^(-) → "NH"_3 + "H"_2"O}$, the ammonium ion accepts an electron pair from the hydroxide ion.

At the moment of collision between the two ions, a lone pair of electrons on the hydroxide ion forms a bond to the $\text{H}$ on the ammonium ion.

Simultaneously, the electron pair on the other side of the $\text{H}$ atom breaks and forms a lone pair on the $\text{N}$ atom.

The electrophilic atom in the${\text{NH}}_{4}^{+}$ is the $\text{H}$ atom.

The ammonium is accepting electrons, so we usually call it a Lewis acid rather than an electrophile