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Chapter 13B Amines and Amides
13.4
Amines
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Amines
Amines
 Are derivatives of ammonia NH3.
 Contain N attached to one or more alkyl or aromatic
groups.
CH3—NH2
CH3

CH3—NH
CH3

CH3—N—CH3
NH2
2
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°
3
Models of Amines
The three-dimensional models show the shapes of
amine molecules with one or more alkyl groups
bonded to the nitrogen atom.
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Publishing as Benjamin Cummings
4
Naming Amines: Common
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
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Naming Amines: IUPAC
In the IUPAC system,
 Amines are named as alkanamines.
 The e in 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
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Naming Amines: IUPAC
2o or 3o amines
 Number longest alkane chain
 Alkyl grps bonded to N are named as N-alkyl grp
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
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Learning Check
Give the common and IUPAC names, and classify as
primary, secondary, or tertiary:
A. CH3—CH2—CH2—NH2
CH3
|
B. CH3—CH2—N—CH3
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Solution
Give the common and IUPAC names, and classify as
primary, secondary, or tertiary:
A. CH3—CH2—CH2—NH2
n-propylamine, 1-propanamine, 1°
CH3
|
B. CH3—CH2—N—CH3
ethyldimethylamine,
N,N-dimethylethanamine, 3°
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Learning Check
Write a structural formula for
A. 2-pentanamine
B.
N-methyl-1-butanamine
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Solution
A.
2-pentanamine
NH2
|
CH3—CH—CH2—CH2—CH3
B.
N-methyl-1-butanamine
CH3—CH2—CH2—CH2—NH—CH3
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Aromatic Amines
 The amine of benzene is aniline.
 Alkyl groups on the N use the prefix N- and the alkyl
name.
NH2
NH2
NH CH3
Cl
Aniline
3-chloroaniline
N-methylaniline
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Learning Check
Give a name for each:
A. CH3—NH—CH2—CH3
B.
C.
CH3
|
CH3—CH2—N—CH2—CH2—CH2—CH3
NH2
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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.
NH2
aniline
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Properties of Amines
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Publishing as Benjamin Cummings
15
Boiling Points:
Alcohols > Amines >Alkanes
of similar mass.
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Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
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.
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Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
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.
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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?
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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
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Amines React as Bases
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
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Neutralization forms Amine Salts
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
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Properties of Amine Salts
Amine salts are
 Solids at room temperature.
 Soluble in water and body fluids.
 The form used for drugs.
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Cocaine
Cocaine
 Is sold illegally as an amine salt.
 Is reacted with NaOH to produce the free amine form
known as “crack”.
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Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Learning Check
Write the equation for ethylamine when it reacts with
each of the following:
1. + H2O
2. + HCl
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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–
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Heterocyclic Amines and Alkaloids
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Publishing as Benjamin Cummings
27
Heterocyclic Amines
A heterocyclic amine
 Is a cyclic organic compound.
 Has a five- or six-atom ring.
 Contains one or more nitrogen atoms.
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Examples of Heterocyclic Amines
N
N
H
Pyrrolidine
N
H
Pyrrole
N
H
Imidazole
N
H
Piperidine
N
N
N
N
N
N
N
H
Pyridine
Pyrimidine
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Publishing as Benjamin Cummings
Purine
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Learning Check
Identify the following heterocyclic amines:
1.
2.
3.
N
N
N
H
H
H
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Solution
Identify the following heterocyclic amines:
1.
2.
3.
N
N
N
H
H
H
1. piperidine
2. pyrrole
3. imidazole
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Alkaloids
Alkaloids are
 Physiologically active nitrogen-containing
compounds.
 Produced by plants.
 Used as stimulants, anesthetics, and
antidepressants.
 Often habit forming.
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Caffeine
Caffeine
 Is a stimulant of the
central nervous
system.
 Is found in coffee
beans, tea,
chocolate, and soft
drinks.
 Contains an
imidazole ring.
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Nicotine
Nicotine
 Increases the adrenaline level in the blood.
 Causes addiction to tobacco.
 Contains a pyrrolidine ring.
N
CH3
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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.
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Morphine and Codeine
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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.
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Pharmacology
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Learning Check
Identify the heterocyclic amine in serotonin.
CH2 CH2 NH2
HO
serotonin
N
H
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Solution
Identify the heterocyclic amine in serotonin.
CH2
HO
CH2
NH2
pyrrole
N
H
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Amides
41
Preparation of Amides
Amides are prepared
 By reacting a carboxylic acid with ammonia or
an amine (1° or 2°).
 Using heat.
O

Heat
CH3—C—OH + NH3
O

CH3—C—NH2 + H2O
O
O

Heat

CH3—C—OH + CH3—NH2
CH3—C—NH—CH3 + H2O
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Amides
In amides, an amino group(–NH2) replaces the –OH
group of carboxylic acids.
O
O
||
||
CH3—C—OH
CH3—C—NH2
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Naming Amides
Amides are named as alkanamides.
 IUPAC replaces –oic acid ending with –amide.
 Common names replace -ic acid ending with –amide.
O

Methanamide (IUPAC)
H—C—NH2
Formamide (common)
O

CH3—CH2—C—NH2
Propanamide (IUPAC)
Propionamide (common)
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Naming Amides with N Groups
 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)
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Aromatic Amides
 The amide of benzene is named benzamide.
O
O
C NH2
C NH CH3
Benzamide
N-methylbenzamide
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Learning Check
Give the IUPAC and common names for the following:
A.
O

CH3–CH2–CH2–C–NH2
B.
O H
 │
CH3–C–N–CH2–CH3
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Solution
A.
B.
O

CH3–CH2–CH2–C–NH2
butanamide; butryamide
OH
 │
CH3–C–N–CH2–CH3
N-ethylethanamide; N-ethylacetamide
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Learning Check
Draw the structures of
A.
pentanamide
B.
N-methylbutyramide
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Solution
A.
pentanamide
O

CH3–CH2–CH2–CH2–C–NH2
B.
N-methylbutyramide
O

CH3–CH2–CH2–C–NH–CH3
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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
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Learning Check
Give the common and IUPAC names for the following
amides and classify as primary, secondary, or tertiary:
A.
O
||
CH3—CH2—CH2—C—NH2
B.
O CH3
|| |
CH3—C—N—CH2—CH3
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Solution
O
||
A. CH3—CH2—CH2—C—NH2
butryamide (common);
butanamide (IUPAC) primary(1°) amide
B.
O CH3
|| |
CH3—C—N—CH2—CH3
N-ethyl-N-methylacetamide (common);
N-ethyl-N-methylethanamide (IUPAC)
tertiary (3°) amide
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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.
54
Some Amides in Health and Medicine
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Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
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.
56
Hydrogen Bonding of Amides
O
||
CH3—C—N—H
|
H
Hydrogen bonding occurs
between primary amides.
O
||
CH3—C—N—H
|
H
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Hydrolysis of Amides
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
58
Hydrolysis of Amides
Amides undergo
acid hydrolysis
base hydrolysis
carboxylic acid
ammonium salt
salt of carboxylic acid
and an amine or ammonia
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Hydrolysis Reactions
acid hydrolysis
O
||
CH3—C—NH2
O
||
CH3—C—OH + NH4+Cl–
HCl + H2O
NaOH
O
||
CH3—C—O– Na+ + NH3
base hydrolysis
60
Learning Check
Write the equation for the hydrolysis of
N-ethylpropanamide with NaOH.
61
Solution
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
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