Question

Why are amines Lewis bases?

Answer 1

Lewis' theory of bases and acids says that:

Acids are lone pair acceptors

Bases are lone pair donors.

A base doesn't lose its lone pair, but shares it, like a dative covalent bond.

An amine has a nitrogen atom connected to three alkyl groups, while also having a lone pair of electrons:

:NR1R2R3, with R1,R2 and R3 being the alkyl groups and : being the lone pair of electrons.

These lone pair of electrons can bond to another molecule by filling a space in an empty orbital.