Download Chapter 16 Carboxylic Acids and Esters

Chapter 16 Carboxylic Acids and
Esters
16.1
Carboxylic Acids
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Carboxylic Acids
A carboxylic acid
Contains a carboxyl group, which is a carbonyl group
(C=O) attached to a hydroxyl group (—OH).
Has the carboxyl group on carbon 1.
carbonyl group
O
||
CH3 — C—OH hydroxyl group or CH3COOH
carboxyl group
2
Models of Carboxylic Acids
The three-dimensional models show the geometry
of atoms in carboxylic acid molecules.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
3
IUPAC Names
The IUPAC names of carboxylic acids
Replace the -e in the alkane name with -oic acid.
methane
CH4
HCOOH
CH3—CH3 ethane
methanoic acid
CH3—COOH ethanoic acid
Number substituents from the carboxyl carbon 1.
CH3
O
║
|
CH3—CH—CH2—C—OH
4
3
2
1
3-methylbutanoic acid
4
Alpha Hydroxy Acids
Alpha hydroxy acids
(AHAs)
Occur naturally in
fruit, milk, and
sugarcane.
Are used in skin
care products.
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Publishing as Benjamin Cummings
5
Names and Sources of Some
Carboxylic Acids
TABLE 16.1
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
6
Aromatic Carboxylic Acids
O
C
OH
O
O
C OH
C OH
Cl
NH2
benzoic acid
3-chlorobenzoic acid
m-chlorobenzoic acid
4-aminobenzoic acid
p-aminobenzoic acid
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Chapter 16 Carboxylic Acids and
Esters
16.2
Properties of Carboxylic Acids
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Publishing as Benjamin Cummings
8
Boiling Points of Carboxylic Acids
The boiling points of carboxylic acids
Are higher than alcohols, ketones, and aldehydes of
similar mass.
Are high because they form dimers in which
hydrogen bonds form between the polar groups in the
two carboxyl groups.
O
H—O
||
|
CH3—C
C—CH3
|
||
O—H
O
A dimer of acetic acid
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Comparison of Boiling Points
Compound
O
║
CH3−CH2−C−H
Molar Mass
Boiling Point
58
49°C
CH3−CH2−CH2−OH
60
97°C
O
║
CH3−C−OH
60
118°C
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Solubility in Water
Carboxylic acids
Form hydrogen
bonds with many
water molecules.
Water molecules
With 1-4 carbon
atoms are very
soluble in water.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
11
Boiling Points and Solubility
TABLE 16.2
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
12
Acidity of Carboxylic Acids
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+
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Publishing as Benjamin Cummings
13
Chapter 16 Carboxylic Acids and
Esters
16.3 Esters
16.4 Naming Esters
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
14
Esters
In an ester,
The H in the carboxyl group is replaced
with an alkyl group.
O
||
CH3 — C—O—CH3
ester group
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
15
Esterification
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
O
||
CH3—C—O—CH2—CH3 + H2O
ethyl acetate (an ester)
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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.
from alcohol
from acid
O
methyl
||
CH3— O—C —CH3
ethanoate (acetate)
IUPAC: methyl ethanoate
common: methyl acetate
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Ester Products
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.
O
C OH
O
O C CH3
O
C O CH3
OH
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Esters in Plants
Esters give
flowers and
fruits their
pleasant
fragrances and
flavors.
TABLE 16.4
19
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Learning Check
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
Give the IUPAC and common names of the following
compound, which is responsible for the flavor and odor
of pears.
from 1-propanol
O
||
CH3—C—O—CH2—CH2—CH3
Propyl ethanoate (IUPAC)
Propyl acetate (common)
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Learning Check
Name the following esters:
O
║
A. CH3—CH2—CH2—C—O—CH3
B.
O
||
CH3—CH2 —C—O—CH2—CH3
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Solution
A. Methyl butanoate (methyl butyrate)
B. Ethyl propanoate (methyl propionate)
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