Chemistry 2100
Lecture 7
Amines
• Amines are nitrogen-containing compounds
Structure and Classification
Amines are classified as 1°, 2°, or 3° depending on
the number of carbon groups bonded to nitrogen.
CH3 -NH2
Methylamine
(a 1° amine)
H
CH3 -N-CH3
Dimethylamine
(a 2° amine)
CH3
CH3 -N-CH3
Trimethylamine
(a 3° amine)
Aliphatic amine: All carbons bonded to nitrogen are
derived from alkyl groups. See the three above.
Aromatic amine: One or more of the groups bonded
to nitrogen are aryl groups.
NH2
Aniline
(a 1° aromatic amine)
H
N-CH3
N-Methylaniline
(a 2° aromatic amine)
CH3
CH2 -N-CH3
Benzyldimethylamine
(a 3° aliphatic amine)
Structure and Classification
– Heterocyclic amine: An amine in which the
nitrogen atom is part of a ring.
– Heterocyclic aliphatic amine: A heterocyclic amine
in which the ring is saturated (has no C=C bonds).
– Heterocyclic aromatic amine: The amine nitrogen
is part of an aromatic ring.
N
N
H
N
H
Pyrrolidine Piperidine
(heterocyclic aliphatic amines)
N
N
N
N
N
N
N
H
H
Pyridine Pyrimidine Imidazole Purine
(heterocyclic aromatic amines)
N
Nomenclature
IUPAC names
– We derive IUPAC names for aliphatic amines just
as we did for alcohols.
– Drop the final -e of the parent alkane and replace it
by -amine.
– Use a number to locate the amino group on the
parent chain.
NH2
CH3 CHCH3
2-Propanamine
NH2
H2 N
Cyclohexanamine
NH2
1,6-Hexan ediamine
Physical Properties
Amines are polar compounds:
– Both 1° and 2° amines have N-H bonds, and can
form hydrogen bonds with one another.
– 3° Amines have no N-H bond and cannot form
hydrogen bonds with one another.
Boiling Points
NH3 (bp -33°C)
CH3CH3 (bp -88°C)
CH3CH2CH2NH2 (bp 48°C)
H2O (bp +100°C)
CH3NH2 (bp -7°C)
CH3OH (bp +65°C)
CH3CH2NHCH3 (bp 35°C)
(CH3)3N (bp 3°C)
Odor
Like ammonia, low-molecular-weight amines
have very sharp, penetrating odors.
– Trimethylamine, for example, is the pungent
principle in the smell of rotting fish.
– Two other particularly pungent amines are 1,4butanediamine (putrescine) and 1,5pentanediamine (cadaverine).
H2N
NH2
1,4-Butanediamine
(Putrescine)
H2N
NH2
1,5-Pentanediamine
(Cadaverine)
Basicity of Amines
Clas s
pK b
Example
H
+
CH3 -N-H :O-H
H
Meth ylammoniu m
hydroxide
: :
: :
H
CH3 -N:
+ H-O-H
H
Methylamin e
(a bas e)
N ame
Aliph atic
Ammonia
3.0 - 4.0 CH3 CH2 NH2
4.74
Ethan amin e Stron ger bas e
Aromatic
8.5 - 9.5 C6 H5 NH2
Anilin e
Weaker base
Ammonium Salts
R'
R N
R"
••
free base
R'
H Cl +
Na OH-
R
N
R"
+
H
ammonium salt
(hydrochloride)
Cl
Alkaloids
H
Cl
N
CH3
N
H
N
H
CH3
H
N
COOCH 3
(S)-(–)nicotine
(S)-(–)-nicotine
CH2 CH2 CH3
H
N
H
(S)(+) -coniine
(S)-(+)-coniine
H
O
H
N
O
O—C
(–)- coca ine hy dr
oc hloride
(–)-cocaine
hydrochloride
H
H
H
O
(–)str y chnine
(–)-strychnine
Nitrosation
NaNO2
+
HCl (aq)
H O N O
+
NaCl (aq)
nitrous acid
R NH2
+
H O N
(1°)
O
HCl
( -2 H2O)
R N N Cl
diazonium
R'
R NH +
(2°)
H2 O
( - HCl )
R OH + N N
salt
R'
H O N
O
HCl
H2O
R N N
nitrosoamine
O
+
H2O
NaNO2
+
HCl (aq)
H O N O
+
NaCl (aq)
nitrous acid
R NH2
+
H O N
(1°)
O
HCl
( -2 H2O)
R N N Cl
diazonium
R'
R NH +
(2°)
H2 O
( - HCl )
R OH + N N
salt
R'
H O N
O
HCl
H2O
R N N
nitrosoamine
O
+
H2O
NaNO2
+
HCl (aq)
H O N O
+
NaCl (aq)
nitrous acid
R NH2
+
H O N
(1°)
O
HCl
( -2 H2O)
R N N Cl
diazonium
R'
R NH +
(2°)
H2 O
( - HCl )
R OH + N N
salt
R'
H O N
O
HCl
H2O
R N N
nitrosoamine
O
+
H2O
NaNO2
+
HCl (aq)
H O N O
+
NaCl (aq)
nitrous acid
R NH2
+
H O N
(1°)
O
HCl
( -2 H2O)
R N N Cl
diazonium
R'
R NH +
(2°)
H2 O
( - HCl )
R OH + N N
salt
R'
H O N
O
HCl
H2O
R N N
nitrosoamine
O
+
H2O
NaNO2
+
HCl (aq)
H O N O
+
NaCl (aq)
nitrous acid
R NH2
+
H O N
(1°)
O
HCl
( -2 H2O)
R N N Cl
diazonium
R'
R NH +
(2°)
H2 O
( - HCl )
R OH + N N
salt
R'
H O N
O
HCl
H2O
R N N
nitrosoamine
O
+
H2O
NaNO2
+
HCl (aq)
H O N O
+
NaCl (aq)
nitrous acid
R NH2
+
H O N
(1°)
O
HCl
( -2 H2O)
R N N Cl
diazonium
R'
R NH +
(2°)
H2 O
( - HCl )
R OH + N N
salt
R'
H O N
O
HCl
H2O
R N N
nitrosoamine
O
+
H2O
NaNO2
+
HCl (aq)
H O N O
+
NaCl (aq)
nitrous acid
R NH2
+
H O N
(1°)
O
HCl
( -2 H2O)
R N N Cl
diazonium
R'
R NH +
(2°)
H2 O
( - HCl )
R OH + N N
salt
R'
H O N
O
HCl
H2O
R N N
nitrosoamine
O
+
H2O
NaNO2
+
HCl (aq)
H O N O
+
NaCl (aq)
nitrous acid
R NH2
+
H O N
(1°)
O
HCl
( -2 H2O)
R N N Cl
diazonium
R'
R NH +
(2°)
H2 O
( - HCl )
R OH + N N
salt
R'
H O N
O
HCl
H2O
R N N
nitrosoamine
O
+
H2O
Azo Dyes
N N Cl
( - HCl )
+
H
NMe2
0°C
N N
B ut te r Yellow
NMe2
N N Cl
( - HCl )
+
H
NMe2
0°C
N N
B ut te r Yellow
NMe2
N N Cl
( - HCl )
+
H
NMe2
0°C
N N
B ut te r Yellow
NMe2
N N Cl
( - HCl )
+
H
NMe2
0°C
N N
B ut te r Yellow
NMe2
OH
H
+
Cl N N
( - HCl )
S O3 H
0°C
OH
N N
Orange II
S O3 H
OH
H
+
Cl N N
( - HCl )
S O3 H
0°C
OH
N N
Orange II
S O3 H
OH
H
+
Cl N N
( - HCl )
S O3 H
0°C
OH
N N
Orange II
S O3 H
OH
H
+
Cl N N
( - HCl )
S O32H
NO
0°C
OH
N N
S O32H
NO
Orange IIFlag Red
American
NH2
OH
OH
N N
HO3 S
SO 3 H
NH2
N N
Direct Bl ue 2B
HO3 S
SO 3 H
NH2
OH
OH
N N
HO3 S
O2 N
N N
Direct Bl ue 2B
SO 3 H
NH2
NH2
HO3 S
SO 3 H
OH
N N
N N
HO3 S
SO 3 H
N N
Diamine G reen B
OH
Heterocyclic Amines
H
••
N
CH3
N
••
N
••
HO
nicotine
••
N
CH2 CH2 CH3
CH3 O
H
H
c oniine
N
••
quinine
CH CH 2
CH 3
CH 3
CH CH 2
CH CH 2
N
CH 3
CH 2CH 3
N
N
Fe
N
CH 3
N
Mg
N
CH 3
CH 3
CH 3
CH 2
CH 2
CH 2
CH 2
COOH
COOH
H
N
CH 3
H
H
CH 3OOC
O
N
O
O
heme
c hlorophyll a
nicotinamide / niacin (B3)
Morphine
Heroin
Codeine
Poison Dart Frogs
N
N
e pibat idine
H
Cl