Download Chapter 13 Carboxylic Acids, Esters, Amines, and Amides

Chapter 13 Carboxylic Acids,
Esters, Amines, and Amides
Carboxylic Acids
A carboxylic acid contains a carboxyl group, which
• is a carbonyl group (C=O) attached to a hydroxyl
group (—OH).
• is found on carbon 1 in carboxylic acids.
13.1
Carboxylic Acids
O
||
CH3 — C—OH hydroxyl group or CH3COOH
carbonyl group
1
2
Names and Sources of Some
Carboxylic Acids
IUPAC Names
In the IUPAC names of carboxylic acids
• the -e in the alkane name is replaced with -oic acid.
CH4
Methane
HCOOH
CH3—CH3 Ethane
Methanoic acid
CH3—COOH Ethanoic acid
• substituents are numbered from the carboxyl carbon 1.
CH3
O
|
║
CH3—CH—CH2—C—OH
4
3
2
1
3-methylbutanoic acid
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4
Aromatic Carboxylic Acids
Common Carboxylic Acids
Benzoic acid
• is the aromatic carboxylic acid.
• locates substituents by numbering the ring from
carbon 1 in the carboxyl group.
methanoic acid (formic acid)
O
║
H─C─OH
ethanoic acid (acetic acid)
O
║
CH3─C─OH
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Learning Check
Solution
A.
Give the IUPAC names of each compound.
A. CH3─CH2─COOH
CH3
|
B. CH3─CH─CH2─COOH
O
C.
C
B.
C.
CH3─CH2─COOH
propanoic acid
CH3
|
CH3─CH─CH2─COOH3-methylbutanoic acid
O
C
OH
3-bromobenzoic acid
OH
Br
Br
7
Chapter 13 Carboxylic Acids,
Esters, Amines, and Amides
8
Polarity of Carboxylic Acids
Carboxylic acids
13.2
Properties of Carboxylic Acids
• are strongly polar.
• have two polar groups:
hydroxyl (−OH) and
carbonyl (C=O).
9
10
Comparison of Boiling Points
Polarity of Carboxylic Acids
Carboxylic acids
• form dimers in which hydrogen bonds form between
two carboxyl groups.
Compound
O
║
CH3−CH2−C−H
O
H—O
||
|
CH3—C
C—CH3
|
||
O—H
O
A dimer of acetic acid
Molar Mass
58
Boiling Point
49 °C
CH3−CH2−CH2−OH
60
97 °C
O
║
CH3−C−OH
60
118 °C
• have higher boiling points than alcohols, ketones, and
aldehydes of similar mass.
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12
Solubility in Water
Carboxylic acids:
• form hydrogen bonds
with many water
molecules.
Boiling Points and Solubility
Water molecules
• with 1-4 carbon
atoms are very
soluble in water.
13
Acidity of Carboxylic Acids
14
Neutralization of Carboxylic Acids
Carboxylic acid salts
• are a product of the neutralization of a carboxylic acid
with a strong base.
CH3—COOH + NaOH
CH3—COO– Na+ + H2O
acetic acid
sodium acetate
Carboxylic acids
• are weak acids.
• ionize in water to produce carboxylate ions
and hydronium ions.
O
O
║
║
CH3−C−OH + H2O
CH3−C−O– + H3O+
(carboxylic acid salt)
• are used as preservatives and flavor enhancers.
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Learning Check
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Solution
Write the equation for the reaction of propanoic acid with
A. water.
Write the equation for the reaction of propanoic acid with
A. water.
CH3—CH2—COOH + H2O
CH3—CH2—COO– + H3O+
B. KOH.
B. KOH.
CH3—CH2—COOH + KOH
17
CH3—CH2—COO– K+ + H2O
18
Chapter 13 Carboxylic Acids,
Esters, Amines, and Amides
Esters
In an ester, the H in the carboxyl group is replaced
with an alkyl group.
13.3
Esters
O
||
CH3 —C—O—CH3
ester group
19
Esterification
20
Learning Check
Esterification is the reaction of
• a carboxylic acid and alcohol in the presence of an
acid catalyst to produce an ester.
O
||
H+
CH3—C—OH + H—O—CH2—CH3
Write the equation for the reaction of propanoic acid
and methanol in the presence of an acid catalyst.
O
||
CH3—C—O—CH2—CH3 + H2O
Ethyl acetate (an ester)
21
Solution
22
Ester Products
Write the equation for the reaction of propanoic acid
and methanol in the presence of an acid catalyst.
O
||
H+
CH3—CH2—C—OH + H—O—CH3
Propanoic acid
Methanol
O
||
CH3—CH2—C—O—CH3 + H2O
Aspirin
• is used to relieve pain and
reduce inflammation.
• is an ester of salicylic acid
and acetic acid.
Oil of wintergreen
• is used to soothe sore
muscles.
• is an ester of salicylic acid
and methanol.
23
O
C OH
O
O C CH3
O
C O CH3
OH
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Naming Esters
Naming Esters
The name of an ester contains the names of
• the alkyl group from the alcohol.
• the carbon chain from the acid with –ate ending.
methyl
ethanoate (acetate)
O
||
CH3— O—C —CH3
Esters are named
• with the alkyl group of the alcohol,
• and the salt (-ate) of the carboxylic acid
From ethanoic
acid (acetic
acid)
IUPAC: methyl ethanoate
common: methyl acetate
From
methanol
(methyl
alcohol)
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Esters in Plants
26
Learning Check
Esters give pleasant fragrances and flavors to many
fruits and flowers.
Give the IUPAC and common names of the following
compound, which is responsible for the flavor and odor
of pears.
O
||
CH3 — C—O—CH2—CH2—CH3
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Solution
28
Learning Check
Give the IUPAC and common names of the following
compound, which is responsible for the flavor and odor
of pears.
Draw the structure of the following compounds.
A. 3-bomobutanoic acid
from 1-propanol
O
||
CH3—C—O—CH2—CH2—CH3
B. Ethyl propionoate
propyl ethanoate (IUPAC)
propyl acetate (common)
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Solution
Acid Hydrolysis of Esters
In acid hydrolysis
• an ester reacts with water to produce a carboxylic acid
and an alcohol.
• an acid catalyst is required.
O
||
H+
H—C—O—CH2—CH3 + H2O
A. 3-bromobutanoic acid
Br
|
CH3—CH—CH2—COOH
B.
Ethyl propionoate
O
||
CH3—CH2 —C—O—CH2—CH3
O
||
H—C—OH
+ H—O—CH2—CH3
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Base Hydrolysis of Fatty Acids
Produces Soaps
Base Hydrolysis (Saponification)
Base hydrolysis or saponification,
• is the reaction of an ester with a strong base.
• produces the salt of the carboxylic acid and an
alcohol.
O
||
CH3—C—O—CH2—CH3 + NaOH
O
||
CH3—C—O– Na+ + HO—CH2—CH3
salt of carboxylic acid
alcohol
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Cleaning Action of Soap
34
Learning Check
A soap
• contains a nonpolar end
that dissolves in nonpolar
fats and oils, and a polar
end that dissolves in
water.
Write the organic products when methyl acetate reacts
with
A. water and an acid catalyst.
B. KOH.
• forms groups of soap
molecules called
micelles that dissolve in
water and are washed
away.
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Chapter 13 Carboxylic Acids,
Esters, Amines, and Amides
Solution
13.4
Amines
Write the organic products when methyl acetate reacts
with
A. water and an acid catalyst.
O
||
CH3—C—OH + HO—CH3
B. KOH.
O
||
CH3—C—O– K+
+ HO—CH3
37
Amines
38
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 bonded
to the nitrogen atom.
• A tertiary (3°) amine has three carbon groups bonded to
the nitrogen atom.
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
H
|
CH3—N—H
1°
CH3
|
CH3—N—H
2°
CH3
|
CH3—N—CH3
3°
39
Models of Amines
40
Naming 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.
The 3-dimensional models show the shapes of amine
molecules with one or more alkyl groups bonded to the
nitrogen atom.
CH3—CH2—NH2
Ethylamine
CH3—NH—CH3
CH3
|
CH3—N—CH2—CH3
Dimethylamine
Ethyldimethylamine
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Learning Check
Solution
Give the common name and classify as
primary, secondary, or tertiary.
A.
CH3—CH2—CH2—NH2
propylamine, 1°
A. CH3—CH2—CH2—NH2
CH3
|
B. CH3—CH2—N—CH3
B.
CH3
|
CH3—CH2—N—CH3
ethyldimethylamine, 3°
43
Aromatic Amines
Learning Check
• The amine of benzene is named aniline.
• Alkyl groups on the N use the prefix N- with alkyl name.
NH2
44
NH2
Give the common name of each compound.
A. CH3—NH—CH2—CH3
NH CH3
B.
Cl
aniline
3-chloroaniline
C.
CH3
|
CH3—CH2—N—CH2—CH3
NH2
N-methylaniline
45
Solution
A.
CH3—NH—CH2—CH3
CH3
|
B. CH3—CH2—N—CH2—CH3
C.
46
Hydrogen Bonding for Amines
The N−H bond
• provides hydrogen bonding in 1°and 2° amines, but
not in 3° amines.
• is not as polar as the O-H bonds in alcohols.
ethylmethylamine
diethylmethylamine
NH2
aniline
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Solubility in Water
Learning Check
Amines
• with 1-6 carbon atoms are soluble in water.
• form hydrogen bonds with the polar O-H bond in water.
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 is soluble in water?
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Solution
50
Amines React as Bases
Like ammonia, amines are weak bases in water.
Consider the following compounds.
1) CH3—CH2—CH2—NH2
2) CH3—CH2—NH—CH3
3) CH3—CH2—CH2—CH3
NH3 + H2O
NH4+ + OH–
ammonium hydroxide
A. Which compound has the highest boiling point?
1) CH3—CH2—CH2—NH2
CH3—NH2 + H2O
CH3—NH3+ + OH–
methylammonium hydroxide
B. Which compound is soluble in water?
1) CH3—CH2—CH2—NH2
2) CH3—CH2—NH—CH3
51
Neutralization Forms Amine Salts
Properties of 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—NH3+ Cl–
CH3—NH2 + HCl
methylamine
52
Amine salts are
• solids at room temperature.
• soluble in water and body fluids.
• the form used for drugs.
methylammonium
chloride
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54
Alkaloids
Cocaine
Alkaloids are
• physiologically active nitrogencontaining compounds.
• obtained from plants.
• used as anesthetics,
antidepressants, and in stimulants
such as caffeine.
• often addictive.
Cocaine (from coca leaves ) is
• sold illegally as the amine salt.
• reacted with NaOH to produce the free
amine form known as “crack.”
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Copyright © 2009 by Pearson Education, Inc.
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Caffeine
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Nicotine
Nicotine
• increases the adrenaline level in the blood.
• causes addiction to tobacco.
Caffeine
• is a stimulant of the
central nervous system.
• is found in coffee beans,
tea, chocolate, and soft
drinks.
N
CH 3
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Morphine and Codeine
58
Learning Check
Morphine and codeine are
• alkaloids.
• obtained from the
oriental poppy plant.
• used as painkillers.
• modified to make heroin.
Write the structural formula for
A.
methylpropylamine
B.
2-chloroaniline
Copyright © 2009 by Pearson Education, Inc.
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Chapter 13 Carboxylic Acids,
Esters, Amines, and Amides
Solution
A.
methylpropylamine
B.
2-chloroaniline
CH3–CH2–CH2–NH–CH3
13.5
Amides
NH2
Cl
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Amides
62
Aromatic Amide
In amides,
• an amino group(–NH2) replaces the –OH group of
carboxylic acids.
O
O
||
||
CH3—C—NH2
CH3—C—OH
The aromatic amine is benzamide.
O
C
NH2
Benzamide
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Preparation of Amides
64
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)
Formamide (common)
H—C—NH2
Amides are produced
• 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
65
O
||
CH3—CH2—C—NH2
Propanamide (IUPAC)
Propionamide (common)
66
Naming Amides with N Groups
Learning Check
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)
Give the IUPAC and common names for the following:
A.
O
||
CH3–CH2–CH2–C–NH2
B.
O H
|| │
CH3–C–N–CH2–CH3
67
Solution
A.
B.
68
Learning Check
O
||
CH3–CH2–CH2–C–NH2
butanamide; butryamide
Draw the structures of
A.
pentanamide.
B.
N-methylbutyramide.
OH
|| │
CH3–C–N–CH2–CH3
N-ethylethanamide; N-ethylacetamide
69
Some Amides in Health and
Medicine
Solution
A.
B.
70
pentanamide
• Urea is the end product of protein metabolism.
O
||
CH3–CH2–CH2–CH2–C–NH2
• Saccharin is an artificial sweetener.
N-methylbutyramide
O
||
CH3–CH2–CH2–C–NH–CH3
• Acetaminophen is used to reduce fever and pain.
• Some amides such as phenobarbital, NembutalTM
and SeconalTM are barbiturates.
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Some Amides in Health and
Medicine
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
O
||
CH3—C—N—H
|
H
74
Hydrolysis of Amides
Amides undergo
• acid hydrolysis to produce a carboxylic acid and
an ammonium salt.
Hydrogen bonding occurs
between primary amides.
• base hydrolysis to produce the salt of a carboxylic
acid and an amine or ammonia.
75
Hydrolysis Reactions
Learning Check
Write the products of the hydrolysis of
N-ethylpropanamide with NaOH.
acid hydrolysis
O
||
CH3—C—NH2
HCl + H2O
NaOH
76
O
||
CH3—C—OH + NH4+Cl–
O
||
CH3—C—O– Na+ + NH3
base hydrolysis
77
78
Solution
Write the products of the hydrolysis of
N-ethylpropanamide with NaOH.
O
||
CH3—CH2—C—O– Na+ + CH3—CH2—NH2
79