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Answer 1 · 2014-12-30T15:29:18

The ammonium ion, #"NH"_4^+#, can act as an electrophile.

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 #"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 #"H"# on the ammonium ion.

Simultaneously, the electron pair on the other side of the #"H"# atom breaks and forms a lone pair on the #"N"# atom.

The electrophilic atom in the#"NH"_4^+# is the #"H"# atom.

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