Chapter 18 · Organic Chemistry
18.16Amines
8 min · two checks
Predict
Why are amines bases?
The idea
- Recognize an amine.
- Explain its basicity.
Amines are derivatives of ammonia in which one, two, or three hydrogens have been replaced by carbon groups: primary RNH₂, secondary R₂NH, tertiary R₃N. They are named with -amine or as alkanamines. Methylamine and trimethylamine are responsible for a lot of “fishy” odor. Because the nitrogen lone pair can take a proton, amines are weak bases, and they form salts with acids. Those salts are often water-soluble and odorless, which is why an acid can tame the smell.
Amines show up in amino acids, in DNA bases, in neurotransmitters, and in countless drugs. Quaternary ammonium ions, four carbons on a positive nitrogen, are not bases in the same way; they have no lone pair left. When you see nitrogen in an organic structure, ask whether it still has a lone pair. That question decides base behavior.
Keep these
- Amines: ammonia with carbon substituents. They are weak bases.
- The lone pair accepts H⁺.
- Many biological molecules are amines.