Amines
No description yet. This curated deck is ready for daily study.
Card preview (24)
Why are amines useful as intermediates in the synthesis of new molecules?
They are very reactive
How do you name amines?
Ending is -amine.
What do you call a benzene ring with a primary amine attached?
Phenylamine
Describe the shape of ammonia.
Pyramidal molecule Bond angle = 107 Lone pairs repel more than bonding pairs
Are amines polar?
Yes
Can primary amines form hydrogen bonds?
Yes using their amine group.
Why are the hydrogen bonds in primary amines weaker than in alcohols?
Nitrogen is less electronegative than oxygen.
What state are shorter chain primary amines at room temperature?
Gases
Describe the solubility of primary amines.
Primary amines with chain lengths up to 4 carbon atoms are very soluble both in water and alcohols because they form hydrogen bonds with these solvents.
What state are longer chain primary amines at room temperature?
Volatile liquids. They have fishy smells.
Why is phenylamine not soluble?
Due to benzene, can’t form hydrogen bonds.
Describe the reactivity of amines.
Amines have a lone pair of electrons. The lone pair of electrons can be used to form a bond with a H+ ion when the amine is acting as a base or an electron-deficient carbon atom when the amine is acting as a nucleophile.
Why are amines Bronsted-Lowry bases?
They can accept a proton.
What is formed when an amine reacts with an acid?
Salts. These are ionic compounds which crystallise as the water evaporates.
What happens if you react a strong base with phenylamine?
It removes the proton from the salt and regenerates the insoluble amine.
What does the strength of a base depend on?
How readily it accepts a proton
What does the lone pair on amines and ammonia do?
Attract protons
Describe the inductive effect.
Alkyl groups release electrons away from the alkyl group and towards the nitrogen atom. This increases the electron density on the nitrogen atom and thus makes it a better electron pair donor (more attracted to protons). Thus primary alkylamines are stronger bases than ammonia.
Why are secondary alkylamines stronger bases than primary alkylamines?
They have 2 R groups so 2 inductive effects.
Why are secondary alkylamines stronger bases than tertiary alkylamines?
Tertiary alyklamines are less soluble in water.
What is the aryl group?
Benzene
Why do aryl groups withdraw electrons from the nitrogen atom?
The lone pair of electrons overlaps with the delocalised system on the benzene ring.
Put these in order of strongest to weakest in terms of bases: phenylamine, ethylamine and ammonia.
Ethylamine>Ammonia>Phenylamine
What do you call a molecule with the group R4N+?
Quaternary ammonium ion