Amines Flashcards
General formula of primary amines
RNH2
General formula of secondary amines
RR’NH
General formula of tertiary amines
RR’R’‘N
What can amines act as?
Bases
Why can amines act as bases?
Lone pair on nitrogen which can accept a proton to form an ammonium ion
What is the strength of a base determined by?
how available the nitrogen lone pair is to accept a proton
What is the positive inductive effect?
Ability of an alkyl group to release electron density through a covalent bond
What is the strongest base?
Tertiary alkyl amine
What is the weakest base?
Tertiary phenyl amine
Why is a tertiary alkyl amine the strongest base?
Due to the positive inductive effect, the alkyl group releases electron density onto the nitrogen
This makes the lone pair on the nitrogen more available to accept a proton
so tertiary alkyl amine is the strongest base
Why is phenyl amine the weakest base?
The lone pair on the nitrogen of phenylamine can delocalise into the pi bond of the phenyl ring
This means it is less available to accept a proton
So phenyl amine is the weakest
Mechanism to form primary amines
Nucleophilic substitution
How to get a higher yield of the primary amine?
Use a large excess ammonia
How to get a higher yield of the quaternary amine?
Use excess haloalkane
Uses of quaternary ammonium salt
Hair conditioner
Fabric softener
These could also be called cationic surfactants
Reduction of nitriles
Haloalkanes undergo nucleophilic substitution with a cyanide ion in ethanolic and aqueous condition
The nitrile formed can then be reduced to an amine functional group which requires hydrogen and a nickel catalyst
Nucleophilic substitution reagent for forming amines from haloalkanes
NH3
Nucleophilic substitution condition for forming amines from haloalkanes
Excess
Nucleophilic substitution problem for forming amines from haloalkanes
Further substitution
Reduction reagent for forming amines from haloalkanes
KCN
H2
Reduction condition for forming amines from haloalkanes
Ethanolic and aqueous
Ni
Reduction problem for forming amines from haloalkanes
KCN is toxic
Two steps so low yield
How is phenylamine formed?
Electrophilic substitution forms nitrobenzene
Nitro group reduced to an amine functional group
HCl and Tin catalyst needed for this reduction
Water can be formed
Uses of amines
Used to make:
dyes
polymers like nylon
drugs and pharmaceuticals
