Chapter Fifteen
Amines
Goals
1. Recognize primary, secondary, tertiary, and
heterocyclic amines
– Recognize quaternary ammonium ions.
2. Name simple amines & write their structures,
3. Describe amines in terms of hydrogen bonding,
solubility, boiling point, and basic nature
4. Be able to predict the products of the acid–base
reactions of amines and ammonium ions.
5. Describe properties of typical of amines.
2
Amines
A compound that has one or
more organic groups bonded
to nitrogen:
3
The importance of the NH4+ ion
• Each amine N atom has
a lone pair of electrons.
– This lone pair is
responsible in large part
for the chemistry of
amines.
•
When a fourth group bonds to the
nitrogen through this lone pair
a quaternary ammonium ion,
which has a permanent positive
charge and forms ionic compounds
with anions.
Amines are Basic
Amines exist as ammonium ions in blood and other
body fluids  resulting in high pH.
aromatic amine
ammonia
non-aromatic amines
Amines are Basic
• Because of the basic nature,
they are often referred to as
Alkaloids
• Man has a long history of
extracting amines from
plants for medicinal and
recreational uses
Codein: A heterocyclic amine
Protein contains amine groups
– Volatile amines produced during decay are responsible
for the odor of rotten fish or decaying meat.
– Cadaver-sniffing dogs are used to detect the strong
odor of the amines produced from decaying flesh.
Some complex amines from plants
can be very poisonous. Many
useful drugs are amines.
Pharmaceutical Amines
Diphenhydramine is an
over-the-counter
antihistamine.
Antihistamines of this type
are oily liquid, and are
converted to amine salts to
be used formulated for use
as medicine
Diphenhydrammonium chloride is also called
Diphenhydramine hydrochloride
Naming Primary Amines
1. Identify the alkyl group attached to nitrogen
– Add the suffix -amine to the alkyl group name
Secondary and Tertiary Amine
Named by adding di- or tri-, to the alkyl
group name along with the suffix -amine.
Dipropylamine
Triethylamine
Classify the amine shown below as primary,
secondary, tertiary, or quaternary.
Primary
Secondary
Tertiary
Quaternary
90%
10%
Qu
at
er
na
ry
ry
Te
rti
a
nd
a
ry
0%
Se
co
ar
y
0%
Pr
im
1.
2.
3.
4.
10
Countdown
Complex 2o and 3o Amines
• The parent compound is chosen as the 1 amine that
contains the largest of the R groups.
• All other groups are are treated as N-substitute groups
•
The largest chain is propane
thus the compound is a
propylamine
•2. It has a ethyl R group :
 we call it N-Ethylpropylamine
Name the amine shown below.
CH3CH2NCH 2CH2CH3
|
CH3
27%
N-ethyl, N-methylpropylamine
N-ethyl, N-propylmethylamine
N-methyl, N-pentylamine
N-methyl, N-propylethylamine
18%
N-
pr
op
y
le
t..
.
in
e
am
et
hy
l,
N-
pe
nt
yl
m
10
N-
lm
et
.. .
et
hy
l,
m
N-
Net
hy
l,
N-
et
hy
l,
N-
m
pr
op
y
et
hy
lp
ro
.. .
9%
N-
1.
2.
3.
4.
45%
Countdown
Who am I?
N-ethyl-N-methyl-N-hexyl amine
N-methyl-N-ethyl hexylamine
N-hexyl-N-methyl ethyl amine
N-ethyl-N-methylhexyl amine
75%
25%
N-
et
hy
l- N
-m
et
. ..
-m
et
.. .
he
xy
l- N
N-
et
hy
l
-m
Nm
et
hy
l- N
0%
-N
-e
th
. ..
et
. ..
0%
N-
1.
2.
3.
4.
Who am I?
1.
2.
3.
4.
N-ethyl-N-methyl-N-hexyl amine
N-methyl-N-ethyl hexylamine
N-hexyl-N-methyl ethyl amine
N-ethyl-N-methylhexyl amine
Aromatic Amine’s
• The simplest aromatic amine
is known by the common
name aniline.
• The methy group is treated as a
substitution onto the Aniline
Amino Group
•
•
–NH2 is also a functional group
(amino group)
when this group is treated as a
substituent amino- is used as
a prefix.
3-Aminopropanoic acid
Properties of Amines
The lone electron pair on the N in amines
causes amines to be weak bases:
.
Electron pair donors that form a bond with H+ in
water
Physical Properties
• Because of hydrogen bonding, 1 and 2 amines have higher boiling points
than alkanes of similar size.
– Amines have less hydrogen bonding, and lower boiling than alcohols of
similar size.
• All amines can hydrogen-bond to water molecules through the lone
electron pair on their nitrogen atoms.
– Amines with up to about 6 C’s are soluble in water.
3 amine molecules have no H atoms attached to N and
therefore cannot hydrogen-bond with each other. As a result
they are much lower boiling than alcohols or 1 or 2 amines
of similar molecular weight.
Heterocyclic Nitrogen Compounds
• Heterocycle: A ring that contains nitrogen or
some other atom in addition to carbon in the ring
structure
• Heterocycles are common in many natural compounds found
in plants and animals.
Heterocyclic Nitrogen compounds
• Look for # of
nitrogen
atoms and #
of carbon
atoms
This compound has 2 nitrogen atoms and 4
carbon atoms
Heterocyclic Nitrogen compounds
• Look for # of
nitrogen
atoms and #
of carbon
atoms
This compound has 4 nitrogen
atoms, and 5 carbon atoms
Basic Nature of Amines
• Amines exist as ammonium ions in the aqueous
environment of blood and other body fluids, which
typically have a pH value of 7.2
• When you see amine compounds represented –
they are normally shown as ions.
Amines are Basic
Amines exist as ammonium ions in blood and other
body fluids  resulting in high pH.
aromatic amine
ammonia
non-aromatic amines
Naming Amine ions
• The positive ions formed by
addition of H+ to alkylamines are
named by replacing the ending –
amine
• by -ammonium.
To name the ions of
heterocyclic amines, the
amine name is modified by
replacing the -e with -ium.
Amine Salts
• Composed of an ammonium cation and an anion
– Ammonium salts are generally odorless, white, crystalline solids
that are much more water-soluble than neutral amines because
they are ionic.
Quaternary
ammonium ions
Permant + charge  structures in
solution that are are unaffected by
changes in pH.
Benzalkonium chlorides, used in surgical
scrubs and storage of surgical instruments
have both antimicrobial and detergent
properties.
Amines in Plants: Alkaloids
1. Naturally occurring, nitrogen-containing compound
isolated from a plant
2. Usually basic, bitter, and poisonous
3. The bitterness and poisonous nature of alkaloids
probably evolved to protect plants from being
devoured by animals.
Physiologically Active Alkaloids
• Caffeine and nicotine are stimulants.
• Others are notable as pain relievers
(analgesics), as sleep inducers, and for the
euphoric states they can create.