Primary, secondary or tertiary?
An amine is a compound that are thought to be derivatives of ammonia, where the hydrogen is replaced with a R group.
- A primary Amine is when a hydrogen is replaced.
- A secondary Amine is when 2 hydrogens are replaced.
- A tertiary Amine is where all 3 hydrogens are replaced.
Naming and Shaping Amines
- All amines are names using the suffix -amine. For example the diagram here shows chloramine. This is an example of a primary amine.
- Because amines are derivatives of ammonia, they keep the pryamidal shape with each bond angle being 107 degrees.
Boiling points and Solubility of amine compounds
- Primary amines with chain lengths up to about 4 carbons are very soluble in water and alcohol. This is due to their polarity which allows them to form hydrogen bonds (Nitrogen has a very high electronegativity).
- Also most amines are soluble in non-polar solvents however Phenylamine is not very soluble in water due to the benzene ring.
- Because amines can partake in hydrogen bonding their boiling points are relativly high.
- However they aren't as high as alchols due to Oxygen being more electronegative and thus having stonger hydrogen bonds.
Amines as bases
- Amines can accept H+ ions (due to the lone pair) and thus are Bronsted-Lowry Bases.
- This means that they'll react with acids to make ionic salts.
- However if a strong base such as NaOH is added then the insoluble amine is made again.
- Ethylamine is the strongest amine base, followed by ammonia and phenylamine being the weakest.
Amines as Nuclophiles
Amines can partake in the reaction above. The lone pair from the amine will attack the electron defficent carbon. The Halogen is then replaced by the amine group (since carbon can only make four bonds).
Amines in industry,
- Amines can be used in fabric conditioners and hair conditioners.
- This is because the quartiary ammonium compounds forms a cation due the positively charged organic group.
- Wet hair and fabric pickes up negative charges and thus this causes a coating preventing static electricity.
Reducing Nitriles to make Amines
Primary Amines can be prepared from haloalkanes in a two step process:
1. Haloalkane reacts with Cynaide ion in ethanol. The cynanide ion replaces the halogen to from a nitrile.
RCl + CN- --> R----C-= N + Cl-
2. The -C-= N functional group is reduced to a primary amine via cataylitic hydrogenation:
R-C=-N + 2 lots of hydrogen gas --> a primary amine.
This is purer than than the nuclophilic subsitution because only a primary amine is made,.
Phenylamine can be made from benzene,
- The benzene reacts with concentrated nitric acid and concentrated sulfuric acid, This produces nitrobenzene (a benzene ring with a NO2 group attached) and water.
- The nitrobenzene is then reduced to phenylamine, using tin and HCl as reducing agents.
This whole equation could be written as