Chapter 16: Amines

• Amines contain one or more organic groups bonded to nitrogen; they have the general formulas RNH2, R2NH, and R3N.

• Amines are organic derivatives of ammonia (NH3). In general, they are classified as primary (1°), secondary (2°), or tertiary (3°), according to how many organic groups are individually bound directly to the nitrogen atom.

• Quaternary ammonium ion is a positive ion with four organic groups bonded to the nitrogen atom (R4N+).

• Properties of amines:

  • Primary and secondary amines can hydrogen-bond with each other and thus are higher boiling than alkanes but lower boiling than alcohols, due to weaker hydrogen bonds.
  • Tertiary amines are lower boiling than secondary or primary amines because hydrogen bonding between tertiary amines is not possible.
  • Methanamine, ethanamine, dimethylamine, and trimethylamine are gases; all other simple amines are liquids.
  • Volatile amines usually have unpleasant odors.
  • Simple amines (those with less than four carbons) are water-soluble due to their ability to hydrogen bonding with water.
  • Amines are weak Bronsted–Lowry/Lewis bases .
  • Many amines are physiologically active, and many are toxic.

• Compounds that contain atoms other than carbon in the ring are known as heterocycles. Heterocyclic nitrogen compounds may be nonaromatic or aromatic. For example, piperidine, is a saturated heterocyclic amine with a six-membered ring.

• Just like ammonia, aqueous solutions of amines are weakly basic because of the formation of OH- and R3NH+ ions in water.

• In terms of basicity:

  • ^^Nonaromatic amines > Ammonia > Aromatic amines^^

• Quaternary ammonium salt is an ionic compound composed of a quaternary ammonium ion and an anion.

• Alkaloid is a naturally occurring, nitrogen-containing compound isolated from a plant. They are usually ^^basic, bitter, and often poisonous^^.

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