An amine is an organic chemical containing a nitrogen atom with tetrahedral arrangement of it electron pairs and its lone pair of electrons. The atoms bonded to nitrogen can be any chemical group except for a carbonyl group. In that case, the compound is called an amide. Amines are related to ammonia (NH3) and have one or more of the protons present in ammonia replaced by a carbon atom. Methylamine, CH3NH2, is the smallest amine. When the nitrogen atom is bonded to one, two, three or four carbon atoms, the chemical is called a primary amine, secondary amine, tertiary amine or quaternary amine, respectively.
The amino group, NH2, is a functional group which serves as a site for chemical reactivity. Amines are basic, like ammonia, meaning that they can accept protons from protic acids or donate electrons to Lewis bases. Thus, dimethylamine (CH3)2NH can be protonated by a strong acid to become a dimethylammonium ion, (CH3)2NH2+. Amines typically have a "fishy" odor.