16 CH105 Carboxylic Acids & Esters
-
Upload
lordniklaus -
Category
Documents
-
view
30 -
download
3
description
Transcript of 16 CH105 Carboxylic Acids & Esters
1
Chapter 16 Carboxylic Acids and Esters
16.1Carboxylic 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—OH 4 3 2 1
3-methylbutanoic acid
IUPAC Names
5
The common names of simple carboxylic acids Are formic acid (1C), acetic acid (2C), propionic acid
(3C), and butyric acid (4C). HCOOH formic acidCH3—COOH acetic acid
Locate substituents using , , γ for the carbon atoms adjacent to the carboxyl carbon. CH3
γ | CH3—CH—CH2—COOH
3-methylbutanoic acid (-methylbutryic acid)
Common Names
6
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
7
Names and Sources of Some Carboxylic Acids
TABLE 16.1
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
8
Common Carboxylic Acids
Methanoic acid (formic acid) O ║
H─C─OH
ethanoic acid (acetic acid) O
║ CH3─C─OH
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
9
Aromatic Carboxylic Acids
Benzoic acid Is the aromatic carboxylic acid. Locates substituents by assigning 1 to the carbon
attached to the carboxyl group. Has common names that assign prefixes ortho,
meta, and para for 2 substituents.ortho 1, 2 locationmeta 1, 3 location para 1, 4 location
10
Aromatic Carboxylic Acids
OHC
O
OHC
O
OHC
O
ClNH2
benzoic acid 3-chlorobenzoic acid 4-aminobenzoic acid m-chlorobenzoic acid p-aminobenzoic acid
11
Give the IUPAC and common names:A. CH3—COOH
CH3
|B. CH3—CH—COOH
C.
Learning Check
COOH
Br
12
A. CH3—COOH ethanoic acid (acetic acid) CH3
|B. CH3—CH—COOH 2-methylpropanoic acid
(-methylpropionic acid)
C. 2-bromobenzoic acid(o-bromobenzoic acid)
Solution
COOH
Br
13
Learning Check
Give the IUPAC and common names for the following:A. CH3─CH2─COOH
CH3
|B. CH3─CH─CH2─COOHC.
OHC
O
Br
14
Solution
A. CH3─CH2─COOH propanoic acid (propionic acid)
CH3
|B. CH3─CH─CH2─COOH 3-methylbutanoic acid
(β-methylbutyric acid)
C. 3-bromobenzoic acid (m-bromobenzoic
acid)
OHC
O
Br
15
Preparation of Carboxylic Acids
Carboxylic acids can be prepared by oxidizing primary alcohols or aldehydes.
The oxidation of ethanol produces ethanoic acid (acetic acid).
OH O O | [O] || [O] ||CH3—CH2 CH3—C—H CH3—C—OH
ethanol ethanal ethanoic acid(ethyl alcohol) (acetaldehyde) (acetic acid)
16
Learning Check
What alcohol could be used to prepare the following:
1. butanoic acid
2. propanoic acid
17
Solution
What alcohol could be used to prepare the following: [O] [O] 1. butanol butanal butanoic acid
[O] [O] 2. 1-propanol propanal propanoic acid
18
16.2 Properties of Carboxylic Acids
Chapter 16 Carboxylic Acids and Esters
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
19
Polarity of Carboxylic Acids
Carboxylic acids Are strongly polar. Have two polar groups:
hydroxyl (−OH) and carbonyl (C=O).
δ-
O ║δ+ δ- δ+
CH3CO H
20
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
21
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
22
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
23
Boiling Points and Solubility
TABLE 16.2
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
24
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
25
Acid Dissociation Constants
Carboxylic acids Have small Ka values. Exist mostly as molecules
and a few ions in aqueous solutions.
TABLE 16.3
26
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 acid salt) Are used as preservatives and flavor enhancers.
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
27
Learning Check
Write the equation for the reaction of propanoic acid withA. water
B. KOH
28
Solution
Write the equation for the reaction of propanoic acid withA. waterCH3—CH2—COOH + H2O CH3—CH2—COO– + H3O+
B. KOH CH3—CH2—COOH + KOH CH3—CH2—COO– K+ + H2O
29
Chapter 16 Carboxylic Acids and Esters
16.3 Esters16.4 Naming Esters
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
30
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
31
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)
Esterification
32
Write the equation for the reaction of propanoic acid and methanol in the presence of an acid catalyst.
Learning Check
33
Write the equation for the reaction of propanoic acidand 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
Solution
34
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
Omethyl
CH3— O—C —CH3
ethanoate (acetate)IUPAC: methyl ethanoatecommon: methyl acetate
35
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
36
Esters in Plants
Esters give flowers andfruits theirpleasant fragrances and flavors.
TABLE 16.4
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
37
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
38
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)
Solution
39
Learning Check
Name the following esters: O ║A. CH3—CH2—CH2—C—O—CH3
O
B. CH3—CH2 —C—O—CH2—CH3
40
Solution
A. Methyl butanoate (methyl butyrate)
B. Ethyl propanoate (methyl propionate)
41
Learning Check
Write the structure of the following esters: A. Ethyl pentanoate
B. Propyl butyrate
42
Solution
A. Ethyl pentanoate O ║
CH3—CH2—CH2—CH2—C—O—CH2—CH3
B. Propyl butyrate
O ║
CH3—CH2—CH2—C—O—CH2—CH2—CH3
43
Chapter 16 Carboxylic Acids and Esters
16.5 Properties of Esters
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
44
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
O H—C—OH + H—O—CH2—CH3
Acid Hydrolysis of Esters
45
Base hydrolysis (also called 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
Base Hydrolysis (Saponification)
46
“Soaps”
The base hydrolysis of long chain fatty acids produces acid salts called “soaps”.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
47
Cleaning Action of SoapA soap Contains a nonpolar
end that dissolves in nonpolar fats and oils, and a polar end that dissolves in water.
Forms groups of soap molecules called micelles that dissolve in water and are washed away.
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
48
Write the organic products when methyl acetate reacts withA. Water and an acid catalyst
B. KOH
Learning Check
49
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
Solution