Amines as nucleophiles and
their synthesis
L.O.:
 Understand the reaction of amines and
ammonia with haloalkanes.
 Know one application of quaternary
ammonium salts.
 Know how amines can be prepared
from nitriles.
 Know how aromatic amines can be
prepared from nitro compounds.
Consider the reaction between ethylamine and
an excess of bromoethane
1. Write the mechanism for the nucleophilic
reaction.
2. Consider what type of product you got.
Would it react with an excess of
bromoethane?
3. Write down all the possible products you
may get in the reaction.
NUCLEOPHILIC SUBSTITUTION
• Lone pair on N can attack + C of haloalkane.
C
X
C
+
NH2
X
-
H
NH3
NH3
C
NH2
NH4+X -
NUCLEOPHILIC SUBSTITUTION
• H on N is swapped by R from haloalkane.
• Product also has lone pair on N so product reacts
further.
H
R
RX
H
N
H
R
RX
H
N
H
R
RX
R
N
H
R
RX
R
N
R
R
• To get mainly 1y amine use XS NH3.
• To get mainly 4y ammonium salt use XS RX.
N
R
R
X
TASK
1) Give all the organic products formed
when
methylamine
reacts
with
chloroethane.
2) Draw the mechanism for the formation
of the tertiary amine in this reaction.
3) Draw all the organic products formed
when diethylamine reacts with 2bromopropane
NUCLEOPHILIC SUBSTITUTION
methylamine + chloroethane
CH3
CH3CH2
(products & 1st mechanism)
CH3
N
CH3CH2
H
CH3
N
CH3CH2
N
CH2CH3
CH2CH3 Cl
CH2CH3
H
CH3
C
CH3
H
CH3CH2
Cl
CH3
- Cl
N
CH3CH2
H
N
CH2CH3
H
CH3
CH3CH2
-H
N
CH3
H
CH3CH2
N
CH2CH3
NUCLEOPHILIC SUBSTITUTION
diethylamine + 2-bromopropane
CH2CH3
CH3CH2
CH3
N
CH
CH3
(products)
CH2CH3
CH3CH2
CH3
N
CH
CH
CH3
CH3
CH3
Br
NUCLEOPHILIC SUBSTITUTION
4y ammonium salts
• Ones with some long chain alkyl groups can be
used as cationic surfactants.
• Often used in fabric softener as many fabrics have
–ve charge on surface.
N
Cl
e.g. (CH3)2N[(CH2)16CH3]2+ Cl-
MAKING ALIPHATIC 1y AMINES
1 – Reaction of NH3 with haloalkanes
• Need to separate mixture of products.
2 – Reduction of nitrile compounds
aqueous ethanol
R
R
or
X
C
+
N
KCN
+
R
4 [H]
+
KX
C
N
R
CH2
NH2
R
CH2
NH2
LiAlH4
Ni
R
C
N
+
2 H2
Give two synthetic paths to making
butylamine. Give equations for all
reactions.
Butylamine
a)
CH3CH2CH2CH2Cl + 2 NH3 → CH3CH2CH2CH2NH2 + NH4Cl
b)
CH3CH2CH2Cl + KCN → CH3CH2CH2CN + KCl
CH3CH2CH2CN + 4 [H] → CH3CH2CH2CH2NH2
MAKING AROMATIC AMINES
NO2
NH2
Sn & HCl
+
6 [H]
+
follow ed
by NaOH
2 H2O