Amines Flashcards
What are amines?
Amines are fishy smelling compounds which contain nitrogen atoms and are derived from ammonia, NH3.
Amines are classified as primary, secondary or tertiary depending on the number of hydrogen atoms in the ammonia that have been replaced by organic groups.
What makes an amine primary, secondary or tertiary???
Amines are classified as primary, secondary or tertiary depending on the number of hydrogen atoms in the ammonia that have been replaced by organic groups.
If 1 hydrogen has been replaced it is a primary amine.
If 2 hydrogens are replaced it is a secondary amine.
If 3 hydrogens are replaced it is a tertiary amine.
What is an aromatic arene?
An amine that contains a benzene ring.
What are the basic properties of amines? (6)
Ammonia, primary amines and primary aromatic amines are bronsted-lowry bases because they can accept protons.
The nitrogen atom in an ammonia molecule has a lone pair of electrons that can accept a hydrogen ion (or proton) to form an ammonium ion
When ammonia dissolves in water it reacts with the water molecules to form an ammonium ion. The solution formed is alkaline because hydroxide ions are formed. However the reaction does not go to completion so ammonia is only a weak base.
Primary amines also dissolve in water to form alkaline solutions
Primary amines are stronger bases than ammonia
Primary aromatic amines such as phenylamine are weaker bases than ammonia
How does ammonia and amines act as nucleophiles?
They have lone pairs of electrons which can be donated to form a dative covalent bond.
What do halagenoalkanes react with an excess of ammonia to form?
Primary amines.
Ethanol is used as a solvent.
If ammonia is not in excess the primary amine produced will react with another halogenoalkane molecule and further substitution can take place.
What does the reactivity of a halogenoalkane depend on?
the strenth of the carbon-halogen bond
this means that fluoroalkanes are least reactive and iodoalkanes are the most reactive.
How are aromatic amines made?
Aromatic amines such as phenylamine can be made by the reducation of nitroarenes such as nitrobenzene using tin and concentrated hydrochloric acid
How are azo dyes made?
By nitrating benzene to produce nitrobenzene.
1) the nitrobenzene is reduced to phenylamine, C6H5NH2, an aromatice amine
2) the aromatic amine is converted to a diazonium salt. Sodium nitrate and HCL are used to produce nitrous acid, HNO2
3) The reaction must be cooled in an ice bath so that it is kept below 10 degrees. This stops the diazonium salt decomposing
4) Finally the diazonium salt is reacted with another suitable aromatic compound to form an azo dye
5) This is a coupling reaaction, Again the reaction must be cooled to stop the diazonium salt from decomposing
how are azo dyes useful?
Azo dyes are useful dyes that can be used to colour synthetic or natural fibres. different coloured dyes are formed by coupling the diazonium salt with different aromatic compounds
