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Lecture 7: Amines and Amides
18.1
Amines
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
2
Amines
Amines Are derivatives of ammonia NH3.
Contain N attached to one or more alkyl or aromatic groups.
CH3 CH3
CH3—NH2 CH3—NH CH3—N—CH3
NH2
3
Classification of Amines
Amines are classified as primary, secondary, or tertiary. In a primary (1°) amine, one carbon group is bonded
to the nitrogen atom. A secondary (2°) amine has two carbon groups. A tertiary (3°) amine has three carbon groups.
H CH3 CH3
| | | CH3—N—H CH3—N—H CH3—N—CH3
1° 2° 3°
4
Models of Amines
The three-dimensional models show the shapes of amine molecules with one or more alkyl groups bonded to the nitrogen atom.
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
5
Naming Simple Amines
Simple amines Are named as alkylamines. List the names of the alkyl groups bonded to the N
atom in alphabetical order in front of amine.
CH3—CH2—NH2 ethylamine
CH3—NH—CH3 dimethylamine
CH3
|CH3—N—CH2—CH3 ethyldimethylamine
6
In the IUPAC system, Amines are named as alkanamines. The ein the alkane name of the longest chain is
changed to amine. The chain is numbered to locate the amine group
and substituents. NH2
| CH3—CH2—NH2 CH3—CH—CH3
Ethanamine 2-Propanamine
IUPAC Names of Amines
7
In a secondary or tertiary amine, The longest alkane chain is numbered. Each alkyl group bonded to the N atom is named as
a N-alkyl group HN—CH3
|CH3—CH2—CH2—NH—CH3 CH3—CH—CH2—CH3
3 2 1 1 2 3 4
N-Methyl-1-propanamine N-Methyl-2-butanamine
Naming Secondary and Tertiary Amines
8
Give the common and IUPAC names, and classify as
primary, secondary, or tertiary:
A. CH3—CH2—CH2—NH2
CH3
|B. CH3—CH2—N—CH3
Learning Check
9
Write a structural formula for
A. 2-pentanamine
B. N-methyl-1-butanamine
Learning Check
10
Aromatic Amines
The amine of benzene is aniline. Alkyl groups on the N use the prefix N-and the alkyl
name.
Aniline 3-chloroaniline N-methylaniline
NH2
Cl
NH2 CH3NH
11
Learning Check
Give a name for each:
A. CH3—NH—CH2—CH3
CH3
|
B. CH3—CH2—N—CH2—CH2—CH2—CH3
C. NH2
12
Solution
A. CH3—NH—CH2—CH3
ethylmethylamine; N-methylethanamine
CH3
|B. CH3—CH2—N—CH2—CH2—CH2—CH3
N-ethyl-N-methyl-1-butanamine
C. aniline
NH2
13
Lecture 7: Amines and Amides
18.2
Properties of Amines
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
14
Boiling Points of Amines, Alcohols, and AlkanesThe boiling points of amines are Higher than alkanes. Lower than alcohols of similar mass.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
15
Hydrogen Bonding for Amines
The polar N-H bond Provides hydrogen bonding in 1°and 2° amines, but
not 3°. In amines is not as polar as the O-H bonds in
alcohols.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
16
Solubility in Water
Amines are soluble in water If they have 1-5 carbon atoms. Because the N atom in smaller amines forms
hydrogen bonds with the polar O-H bond in water.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
17
Learning Check
Consider the following compounds:
1. CH3—CH2—CH2—NH2
2. CH3—CH2—NH—CH3
3. CH3—CH2—CH2—CH3
A. Which compound has the highest boiling point?
B. Which compound(s) is(are) soluble in water?
18
Solution
Consider the following compounds:1. CH3—CH2—CH2—NH2
2. CH3—CH2—NH—CH3
3. CH3—CH2—CH2—CH3
A. Which compound has the highest boiling point?1. CH3—CH2—CH2—NH2
B. Which compound(s) is(are) soluble in water?1. CH3—CH2—CH2—NH2
2. CH3—CH2—NH—CH3
19
Amines are Bronsted-Lowry bases that attract a H+ from H2O
to the N atom. Weak bases in water.
NH3 + H2O NH4+ + OH–
ammonium hydroxide
CH3—NH2 + H2O CH3—NH3+ + OH–
methylammonium hydroxide
Amines React as Bases
20
An amine salt Forms when an amine is
neutralized by acid. Is named by replacing the amine
part of the name with ammonium followed by the name of the negative ion.
CH3—NH2 + HCl CH3—NH3+Cl–
methylamine methylammonium chloride
Neutralization forms Amine Salts
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
21
Properties of Amine Salts
Amine salts are Solids at room temperature. Soluble in water and body fluids. The form used for drugs.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
22
Cocaine
Cocaine Is sold illegally as an amine salt. Is reacted with NaOH to produce the free amine form
known as “crack”.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
23
Learning Check
Write the equation for ethylamine when it reacts with
each of the following:
1. + H2O
2. + HCl
24
Solution
Write the equation for ethylamine when it reacts with
each of the following:
1. CH3—CH2—NH2 + H2O CH3—CH2—NH3+ OH–
2. CH3—CH2—NH2 + HCl CH3—CH2—NH3+ Cl–
25
Lecture 7: Amines and Amides
18.3
Heterocyclic Amines and Alkaloids
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
26
Heterocyclic Amines
A heterocyclic amine Is a cyclic organic compound. Has a five- or six-atom ring. Contains one or more nitrogen atoms.
27
Examples of Heterocyclic Amines
N
NN
N
N
H
N
H
N
H
Pyrrolidine Pyrrole
Piperidine Pyridine Pyrimidine
N
N
N
N
H
Purine
N
H
Imidazole
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
28
Learning Check
Identify the following heterocyclic amines:
1. 2. 3.
N
H
N
H
N
H
29
Solution
Identify the following heterocyclic amines:
1. 2. 3.
1. piperidine 2. pyrrole 3. imidazole
N
H
N
H
N
H
30
Alkaloids are Physiologically active nitrogen-containing
compounds. Produced by plants. Used as stimulants, anesthetics, and
antidepressants. Often habit forming.
Alkaloids
31
Caffeine
Caffeine Is a stimulant of the
central nervous system. Is found in coffee
beans, tea, chocolate, and soft drinks.
Contains an imidazole ring.
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
32
Nicotine
Nicotine Increases the adrenaline level in the blood. Causes addiction to tobacco. Contains a pyrrolidine ring.
N
CH3
33
Alkaloids Related to Morphine
Alkaloids Such as morphine and codeine are produced by the
poppy. Have been used for centuries as painkillers. Such as heroin and codeine are modifications of
morphine.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
34
Morphine and Codeine
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
35
Pharmacology
An area of research in pharmacology Is to design drugs such as procaine, lidocaine, and
demerol that retain some of the characteristics of alkaloids.
Is to modify the structures of cocaine and morphine to produce anesthesia, but without the addictive side effects.
36
Pharmacology
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
37
Learning Check
Identify the heterocyclic amine in serotonin.
serotonin
HO
N
H
CH2 CH2 NH2
38
Solution
Identify the heterocyclic amine in serotonin.
pyrrole
N
HOCH2
H
CH2 NH2
39
18.4
Amides
Lecture 7: Amines and Amides
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
40
Preparation of Amides
Amides are prepared By reacting a carboxylic acid with ammonia or
an amine (1° or 2°).
Using heat. O O Heat CH3—C—OH + NH3 CH3—C—NH2 + H2O
O O Heat CH3—C—OH + CH3—NH2 CH3—C—NH—CH3 + H2O
41
In amides, an amino group(–NH2) replaces the –OH group of carboxylic acids.
O O || ||
CH3—C—OH CH3—C—NH2
Amides
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
42
Amides are named as alkanamides. IUPAC replaces –oicacidendingwith –amide. Common names replace -icacid ending with –amide. O Methanamide (IUPAC) H—C—NH2 Formamide (common)
O Propanamide (IUPAC) CH3—CH2—C—NH2 Propionamide (common)
Naming Amides
43
An alkyl group bonded to the N atom is named as N-alkyl in front of the amide name.
O H │ CH3 —C—N—CH3 N-methylethanamide (IUPAC)
N-methylacetamide (common) O H │ CH3—CH2 —C—N—CH2—CH3
N-ethylpropanamide (IUPAC) N-ethylpropionamide
(common)
Naming Amides with N Groups
44
Aromatic Amides
The amide of benzene is named benzamide.
C
O
NH2
Benzamide
C
O
NH CH3
N methylbenzamide -
45
Learning Check
Give the IUPAC and common names for the following:
O A. CH3–CH2–CH2–C–NH2
O H │B. CH3–C–N–CH2–CH3
46
Solution
O A. CH3–CH2–CH2–C–NH2
butanamide; butryamide
O H │B. CH3–C–N–CH2–CH3
N-ethylethanamide; N-ethylacetamide
47
Learning Check
Draw the structures of
A. pentanamide
B. N-methylbutyramide
48
Solution
A. pentanamideO
CH3–CH2–CH2–CH2–C–NH2
B. N-methylbutyramide O
CH3–CH2–CH2–C–NH–CH3
49
Classification of Amides
Amides are classified according to the number of carbon atoms bonded to the nitrogen atom.
O H || | CH3—C—N—H Primary (1°) amide
O H || | CH3—C—N—CH3 Secondary (2°) amide
O CH3 || | CH3 —C—N—CH3 Tertiary (3°) amide
50
Give the common and IUPAC names for the followingamides and classify as primary, secondary, or tertiary:
O || A. CH3—CH2—CH2—C—NH2
O CH3 || |B. CH3—C—N—CH2—CH3
Learning Check
51
O ||A. CH3—CH2—CH2—C—NH2
butryamide (common); butanamide (IUPAC) primary(1°) amide
O CH3 || | B. CH3—C—N—CH2—CH3
N-ethyl-N-methylacetamide (common);
N-ethyl-N-methylethanamide (IUPAC)
tertiary (3°) amide
Solution
52
Some Amides in Health and Medicine Urea is the end product of protein metabolism.
Saccharin is an artificial sweetener.
Some amides such as phenobarbital, Nembutal and Seconal are barbiturates.
Acetaminophen is used to reduce fever and pain.
53
Some Amides in Health and Medicine
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
54
Physical Properties of Amides
Amides That are primary (−NH2) or secondary (−NH−) form
hydrogen bonds. That are primary have higher melting points than
secondary. That are tertiary (no H on N) do not form hydrogen
bonds and have lower melting points. All form hydrogen bonds with water. With 1-5 carbon atoms are soluble in water.
55
Hydrogen Bonding of Amides
O || CH3—C—N—H | H Hydrogen bonding occurs
between primary amides. O ||
CH3—C—N—H |
H
56
18.5
Hydrolysis of Amides
Lecture 7: Amines and Amides
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
57
Hydrolysis of Amides
Amides undergo
acid hydrolysis base hydrolysis
carboxylic acid salt of carboxylic acid
ammonium salt and an amine or ammonia
58
acid hydrolysis O
|| O CH3—C—OH + NH4
+Cl–
|| HCl + H2O CH3—C—NH2
NaOH O ||
CH3—C—O– Na+ + NH3
base hydrolysis
Hydrolysis Reactions
59
Write the equation for the hydrolysis of
N-ethylpropanamide with NaOH.
Learning Check
60
Write the products of the hydrolysis of
N-ethylpropanamide with NaOH.
O CH3—CH2—C—N—CH2—CH3 + NaOH
N-ethylpropanamide
O CH3—CH2—C—O– Na+ + CH3—CH2—NH2
Solution
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