Transcript Chapter 10: Amines

CHAPTER 10: AMINES
AMINES
Nitrogen containing compound
 Nitrogen is a group 5A element with 5 valence
electrons
 Nitrogen has 3 bonds and 1 lone pair
 Ammonia derivatives where at least one H is
replaced by an alkyl, cycloalkyl, or aryl group

•
Amines are organic nitrogen compounds, formed
by replacing one or more hydrogen atoms of
ammonia (NH3) with alkyl groups.
•
Amines are classified as 10, 20, or 30 based on the
number of alkyl groups bonded to the nitrogen
atom.
Amines
Structure and Bonding
• An amine N atom is sp3 hybridized and trigonal pyramidal, with
bond angles of approximately 109.50.
• Since an amine nitrogen has four different groups around it, it is
technically a stereocenter.
Amines
Structure and Bonding
• However, the chirality of the amine nitrogen can be ignored
because the two enantiomers interconvert by passing through a
trigonal planar (achiral) transition state.
Amines
Structure and Bonding
• In contrast, the chirality of a quaternary ammonium salt with four
different groups cannot be ignored. Because there is no
nonbonded electron pair on the nitrogen atom, interconversion
cannot occur, and the N atom is just like a carbon atom with four
different groups around it.
STRUCTURE OF AMINES
Aliphatic amines
N bonded to alkyl
groups
CH3NHCH2CH3
Aromatic Amines
N bonded to one or more
aryl groups
NH2
N
CH3
CH3
|
CH3CH2NCH3
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HETEROCYCLIC AMINES

Heterocyclic aliphatic
amines


Ring is saturated and N
is part of a non
aromatic ring
Heterocyclic aromatic
amines

When nitrogen is part
of an aromatic ring
N
N
H
Pyrrolidine
N
H
Pyrrole
N
H
Imidazole
N
H
Piperidine
N
N
N
N
N
N
N
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H
Pyridine
Pyrimidine
Purine
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NAMING AMINES
Amines may be named using either common or IUPAC
rules
 For common names, list the alkyl groups attached to
the N in ABC order and use the suffix –amine, which is
written as one word
 Prefixes di- and tri- are used if identical groups are
present

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IUPAC NAMING OF 1O AMINES
1. Select the longest carbon chain that contains the N
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as the parent
2. Name parent as an alkan-amine by removing the –e
of the alkane and replacing it with the suffix –amine
3. # the parent from the end nearest the N
4. The location of the amino group comes before the
parent
5. If the parent is substituted, its name and # comes
before the parent
NOMENCLATURE
IUPAC NAMING 1O AMINES

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Compounds with 2 amino groups are named by adding
suffix -diamine. The final ‘e’ of the parent hydrocarbon is
retained
NH
2
|
H2NCH2CH2CH2CH2CH2CH2NH2
CH CHCH2NH2
1,6-hexanediamine
3
1,2- propanediamine
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IUPAC NAMING 2O AND 3O
AMINES
1.
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2o and 3o amines are named as N-substituted primary
amines
The largest alkyl chain is considered the parent
The other alkyl chains are placed in front of the parent
using the prefix N- to denoted that it is attached to the N
2.
3.
CH3NHCH2CH3
N- methylethanamine
N,N-dimethylcyclohexanamine
N(CH3)2
CH3—CH2—CH2—NH—CH3
3
2
1
N-Methyl-1-propanamine
HN—CH3
|
CH3—CH—CH2—CH3
1
2
3
4
N-Methyl-2-butanamine
CH — NH — CH
3
3
N - methylmethanamine
( d imethylamine
NH2
)
NH CH3
N - methylaniline
Aniline
NOMENCLATURE PRIORITY
If other functional groups are present on an
amine, the –NH2 group is a substituent and is
called –amino
 Priority List from highest to lowest:
carboxylic acid, aldehyde, ketone,
alcohol, amine

Learning Check
Give the name and classify:
A. CH3NHCH2CH3
CH3
|
B. CH3CH2NCH3
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Solution
A. CH3NHCH2CH3
N-methylethanamine , 2°
CH3
|
B. CH3CH2NCH3
N,N- dimethylethanamine , 3°
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Solution
A.
B.
1-pentanamine
CH3CH2CH2CH2CH2-NH2
1,3-cyclohexanediamine
NH2
NH2
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PHYSICAL PROPERTIES
•
•
•
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•
Amines are polar compounds
Both 1° and 2° amines form hydrogen bonds
Boiling points are higher than corresponding alkanes but
lower than the corresponding alcohols
Are soluble if 6 or less carbons are present
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BOILING POINTS
N-H less polar than O-H.
 Weaker hydrogen bonding.
 Tertiary amines cannot hydrogen bond.

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PHYSICAL PROPERTIES OF AMINES
Boiling points of amines are higher than those
of alkanes but lower than those of alcohols
Compound
CH3CH3
Formula Mass
30
BP(oC)
-89
CH3NH2
31
-6
CH3OH
32
65
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BASICITY OF AMINES
Lone pair of electrons on nitrogen can accept a proton
from an acid
 All amines are weak bases and aqueous solutions of
amines are basic

Hydroxide
ion
H
Methylamine
+
H-O-H
••
CH
3
+
-N -H
+
-
••
O-H
••
3
-N
••
CH
••
••
H
Methylammonium ion
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Amines
Interesting and Useful Amines
• Many low molecular weight amines have foul odors.
• Trimethylamine [(CH3)3N], formed when enzymes break
down certain fish proteins, has the characteristic odor of
rotting fish.
• Putrescine (NH2CH2CH2CH2CH2NH2) and cadaverine
(NH2CH2CH2CH2CH2CH2NH2) are both poisonous diamines
with putrid odors. They too are present in rotting fish, and
are partly responsible for the odors of semen, urine, and bad
breath.
• Naturally occurring amines derived from plant sources are
called alkaloids.
Amines
Interesting and Useful Amines
• Histamine, a rather simple triamine that is
present in many tissues, is responsible for a wide
variety of physiological effects.
• Understanding the physiological properties of
histamine has helped chemists design drugs to
counteract some of its undesirable effects. Antihistamines bind to the
same active site as histamine in the cell, but they evoke a different
response. Examples are brompheniramine and cimetidine.
Amines
Interesting and Useful Amines
• A large number of physiologically active compounds are derived from
2-phenethylamine (C6H5CH2CH2NH2). These compounds include
adrenaline, noradrenaline, methamphetamine, and mescaline. Each
contains a benzene ring bonded to a two-carbon unit with a nitrogen
atom (shown in red).
NEUROTRANSMITTERS

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Neurotransmitter – chemical substance that is released at
the end of a nerve, travels across the synaptic gap, and
then bonds to a receptor site on another nerve, causing a
nerve impulse
OH
NH2
HO
NH2
HO
Dopamine
Norepinephrine
HO
HO
OH
HO
H
N
Epinephrine
NH2
N
N
Histamine
HO
H
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Amines
Natural and Synthetic Dyes
• Three natural dyes known for centuries are indigo, tyrian purple, and alizarin.
Amines
Sulfa Drugs
• In 1935, Gerhard Domagk first used a synthetic dye, prontosil, to kill bacteria.
• Prontosil and other sulfur containing antibiotics are collectively known as sulfa
drugs.
• Prontosil is not the active ingredient itself—In cells, it is metabolized to
sulfanilamide, the active drug.
Amines
Sulfa Drugs
• To understand how sulfanilamide functions as an antibacterial
agent, we must examine folic acid, which microorganisms
synthesize from p-aminobenzoic acid.
• Sulfanilamide and p-aminobenzoic acid are similar in size and
shape and have related functional groups.
Amines
Sulfa Drugs
• When sulfanilamide is administered, bacteria attempt to use it in
place of p-aminobenzoic acid to synthesize folic acid. Derailing
folic acid synthesis means that the bacteria cannot grow and
reproduce. Sulfanilamide only affects bacterial cells, because
humans do not synthesize folic acid, and must obtain it from their
diets.