Amines are organic compounds derived from ammonia (NH₃), in which one or more of the hydrogen atoms are replaced by alkyl groups (R–) or aryl groups (Ar–).
They can be thought of as “derivatives of ammonia” where the nitrogen atom has a lone pair of electrons, making them basic and often nucleophilic.
Classification of Amines
Based on how many hydrogens of ammonia are replaced:
- Primary amine (1°): one hydrogen replaced → R–NH₂
Example: methylamine (CH₃NH₂) - Secondary amine (2°): two hydrogens replaced → R₂–NH
Example: dimethylamine ((CH₃)₂NH) - Tertiary amine (3°): all three hydrogens replaced → R₃–N
Example: trimethylamine ((CH₃)₃N)
If one or more R groups are aromatic (aryl), the amine is called an aromatic amine (e.g., aniline, C₆H₅NH₂).
Key Properties
- Basicity: Due to the lone pair on nitrogen, they can accept protons.
- Solubility: Lower amines are soluble in water (hydrogen bonding); higher ones are less soluble.
- Odor: Many low-molecular-weight amines have a “fishy” smell.
- Reactivity: They undergo alkylation, acylation, and form salts with acids.
Importance
- Found in many biological molecules (neurotransmitters like dopamine, serotonin).
- Used in dyes, drugs, polymers, and agrochemicals.