Here’s a clear explanation of how amines are prepared without using chemical equations:
1. From Alkyl Halides
Amines can be made by reacting an alkyl halide with ammonia or another amine. The nitrogen from ammonia replaces the halogen. Using excess ammonia usually gives primary amines, while further reactions can produce secondary and tertiary amines.
2. Reduction of Nitrogen-Containing Compounds
- Nitro compounds can be converted to amines by using a reducing agent like hydrogen with a catalyst or metals in acidic conditions.
- Nitriles (compounds with a carbon triple-bonded to nitrogen) can be reduced to amines.
- Amides (compounds with a carbonyl attached to nitrogen) can also be reduced to form amines.
3. Reductive Amination of Carbonyl Compounds
Aldehydes or ketones can react with ammonia or amines to first form an intermediate called an imine. This intermediate is then reduced to form an amine. This method works for making primary, secondary, or tertiary amines depending on the starting materials.
4. Gabriel Phthalimide Synthesis
This method is specifically used to prepare primary amines. Phthalimide is first converted to a reactive form, which then reacts with an alkyl halide. Finally, it is hydrolyzed to release the primary amine.
5. From Azides
Organic azides can be converted to amines by reduction. There’s also the Curtius rearrangement, where a carboxylic acid is transformed into an amine through an intermediate called an isocyanate.
6. Hofmann Rearrangement
Amides can be converted into primary amines that have one carbon fewer than the original amide.
These are the main ways chemists prepare amines in the lab, and each method is chosen based on the type of amine desired (primary, secondary, or tertiary).