Download Chapter 18 Amines and Amides

Chapter 18 Amines and Amides
18.1
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.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
4
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
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IUPAC Names of Amines
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 Secondary and Tertiary
Amines
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
N-Methyl-1-propanamine
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
A.
B.
CH3—CH2—CH2—NH2
1-propylamine, 1-propanamine, 1°
CH3
|
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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Chapter 18 Amines and Amides
18.2
Properties of Amines
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
15
Boiling Points of Amines,
Alcohols, and Alkanes
The boiling points of amines are
Higher than alkanes.
Lower than alcohols of similar mass.
16
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.
17
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.
18
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
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
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
22
Properties of Amine Salts
Amine salts are
Solids at room temperature.
Soluble in water and body fluids.
The form used for drugs.
23
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Cocaine
Cocaine
Is sold illegally as an amine salt.
Is reacted with NaOH to produce the free amine form
known as “crack”.
24
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
25
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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Chapter 18 Amines and Amides
18.4
Amides
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
27
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
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
29
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
34
Learning Check
Draw the structures of
A.
pentanamide
B.
N-methylbutyramide
35
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
37
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.
40
Some Amides in Health and Medicine
41
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.
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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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