Chapter 16 Carboxylic Acids and Esters - Cerritos...
Transcript of Chapter 16 Carboxylic Acids and Esters - Cerritos...
1
Chapter 16 Carboxylic Acids and
Esters
16.1
Carboxylic Acids
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
2
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
Carboxylic Acids
3
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
4
The IUPAC names of carboxylic acids
� Replace the -e in the alkane name with -oic acid.
CH4 methane HCOOH methanoic acid
CH3—CH3 ethane CH3—COOH ethanoic acid
� Number substituents from the carboxyl carbon 1.
CH3 O| ║
CH3—CH—CH2—C—OH4 3 2 1
3-methylbutanoic acid
IUPAC Names
5
Alpha Hydroxy Acids
Alpha hydroxy acids
(AHAs)
� Occur naturally in fruit, milk, and
sugarcane.
� Are used in skin
care products.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
6
Names and Sources of Some
Carboxylic Acids
TABLE 16.1
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
7
Aromatic Carboxylic Acids
OHC
O
OHC
O
OHC
O
ClNH2
benzoic acid 3-chlorobenzoic acid 4-aminobenzoic acid
m-chlorobenzoic acid p-aminobenzoic acid
8
16.2 Properties of Carboxylic Acids
Chapter 16 Carboxylic Acids and
Esters
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
9
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
10
Comparison of Boiling Points
Compound Molar Mass Boiling Point
O
║CH3−CH2−C−H 58 49°C
CH3−CH2−CH2−OH 60 97°C
O
║CH3−C−OH 60 118°C
11
Solubility in Water
Carboxylic acids
� Form hydrogen
bonds with many water molecules.
� With 1-4 carbon
atoms are very
soluble in water.
Water molecules
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
12
Boiling Points and Solubility
TABLE 16.2
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
13
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
+
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
14
Chapter 16 Carboxylic Acids and
Esters
16.3 Esters
16.4 Naming Esters
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
15
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
16
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 + H2Oethyl acetate (an ester)
Esterification
17
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
18
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.
CH3
O
CO
OH
O
C
OH
CH3O
O
C
19
Esters in Plants
Esters give flowers and
fruits their
pleasant
fragrances and
flavors.
TABLE 16.4
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
20
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
21
Give the IUPAC and common names of the following compound, which is responsible for the flavor and odor of pears.
from 1-propanolO||
CH3—C—O—CH2—CH2—CH3
Propyl ethanoate (IUPAC)
Propyl acetate (common)
Solution
22
Learning Check
Name the following esters:O
║A. CH3—CH2—CH2—C—O—CH3
O||
B. CH3—CH2 —C—O—CH2—CH3
23
Solution
A. Methyl butanoate (methyl butyrate)
B. Ethyl propanoate (methyl propionate)