Primary and secondary amines
Primary and secondary amines
- An amine has an –NH₂ group (primary) or –NH– (secondary).
- They are made several ways.
- They are weak bases, thanks to the nitrogen lone pair.
Practice
A primary amine has the group:
A primary amine has –NH₂; a secondary amine has –NH– between two carbons.
Making amines
- a halogenoalkane + NH₃ (ethanol, pressure) → a primary amine.
- a halogenoalkane + a primary amine → a secondary amine.
- reduction of an amide or nitrile with $\text{LiAlH}_4$.
- an amine (or ammonia) + an acyl chloride → an amide.
Practice
A primary amine is made by heating a halogenoalkane with:
Ammonia substitutes the halogen to give the amine (excess NH₃ favours the primary amine).
Practice
Reducing a nitrile or amide with LiAlH₄ gives:
LiAlH₄ reduces both nitriles and amides to amines.
Basicity
- The lone pair on the nitrogen can accept an $\text{H}^+$ — this makes amines bases.
Practice
Amines are bases because:
The nitrogen lone pair accepts H⁺, making the amine a base.
You've got it
Key idea
- amine = –NH₂ (1°) or –NH– (2°)
- made from halogenoalkane + NH₃, or by reducing a nitrile/amide ($\text{LiAlH}_4$)
- amines are bases — the nitrogen lone pair accepts $\text{H}^+$