28.1 Introduction to amines Flashcards
In what way are amines related to ammonia
They are derivatives of ammonia where one or more hydrogen atoms in ammonia have been replaced by alkyl or aryl
So all have a nitrogen with a lone pair
N:
What are primary, secondary and tertiary amines
Primary amine is ammonia with one hydrogen swapped for an alkyl group.
So general formula RNH2
Secondary is ammonia with two hydrogens swapped for two alkyl groups
Tertiary is ammonia with three hydrogens swapped for three alkyl groups
How are amines named
When a CH2 is added to amine it is called methylamine
When ethane CH3CH2 is added it is ethylamine
Then if two methyls are added it is dimethylamine
When a benzene is added it is phenylamine
What shape is ammonia and what is the bond angle
Ammonia is a 107 degree bond angle because it could be a tetrahedral which is 109.5 degrees, and one lone pair squishes it to 107 degrees.
So it is a trigonal pyramidal shape
Describe boiling points of amines
Amines are polar, eg N is f- and H is f+.
So they can hydrogen bond to each other using their NH2 groups.
However nitrogen is less electronegative than oxygen, so compared to alcohols (where hydrogen bonding is O-H) the hydrogen bonding is weaker
This means boiling points of amines are lower than of alcohols
How do longer chain amines smell
They smell like rotten fish
Describe the solubility of amines
What about phenylamines
Primary amines with chains up to 4 carbon atoms are very soluble in both water and in alcohols.
This is because they can form hydrogen bonds with these solvents
Most amines are also soluble in less polar solvents
Phenylamines however are not soluble due to benzene ring which can’t form hydrogen bonds
Describe reactivity of amines
Amines have a lone pair of electrons on the nitrogen.
The lone pair can form a bond with:
- A H+ ion when the amine is acting as a base ( as bases are proton acceptors)
- Also form a bond with an electron deficient carbon atom, when the amine is acting as a nucleophile
