1 Chapter 16 Carboxylic Acids and Esters
16.1 Carboxylic Acids Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
2 Carboxylic Acids O 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
3 Models of Carboxylic Acids
The three-dimensional models show the geometry of atoms in carboxylic acid molecules. Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
4 IUPAC Names 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. CH O | ║ CH3—CH—CH2—C—OH 3-methylbutanoic acid
5 Common Names The common names of simple carboxylic acids
Are formic acid (1C), acetic acid (2C), propionic acid (3C), and butyric acid (4C). HCOOH formic acid CH3—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)
6 Alpha Hydroxy Acids Alpha hydroxy acids (AHAs)
Occur naturally in fruit, milk, and sugarcane. Are used in skin care products. Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
7 Names and Sources of Some Carboxylic Acids
TABLE 16.1 Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
8 Common Carboxylic Acids
Methanoic acid (formic acid) O ║ H─C─OH ethanoic acid (acetic acid) CH3─C─OH Copyright © 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 location meta 1, 3 location para 1, 4 location
10 Aromatic Carboxylic Acids
benzoic acid chlorobenzoic acid aminobenzoic acid m-chlorobenzoic acid p-aminobenzoic acid
11 Learning Check Give the IUPAC and common names: A. CH3—COOH CH3 |
B. CH3—CH—COOH C.
12 Solution A. CH3—COOH ethanoic acid (acetic acid) CH3 |
B. CH3—CH—COOH 2-methylpropanoic acid (-methylpropionic acid) C bromobenzoic acid (o-bromobenzoic acid)
13 Learning Check Give the IUPAC and common names for the following:
A. CH3─CH2─COOH CH3 | B. CH3─CH─CH2─COOH C.
14 Solution A. CH3─CH2─COOH propanoic acid (propionic acid) CH3 |
B. CH3─CH─CH2─COOH methylbutanoic acid (β-methylbutyric acid) C bromobenzoic acid (m-bromobenzoic acid)
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—CH 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 Chapter 16 Carboxylic Acids and Esters
16.2 Properties of Carboxylic Acids Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
19 Polarity of 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 °C CH3−CH2−CH2−OH °C CH3−C−OH °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 © by Pearson Education, Inc. Publishing as Benjamin Cummings
23 Boiling Points and Solubility
TABLE 16.2 Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
24 Acidity of 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 © by Pearson Education, Inc. Publishing as Benjamin Cummings
25 Acid Dissociation Constants
TABLE 16.3 Carboxylic acids Have small Ka values. Exist mostly as molecules and a few ions in aqueous solutions.
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 © by Pearson Education, Inc. Publishing as Benjamin Cummings
27 Learning Check Write the equation for the reaction of propanoic acid with A. water B. KOH
28 Solution Write the equation for the reaction of propanoic acid with
A. water CH3—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
16.4 Naming Esters Copyright © 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 © by Pearson Education, Inc. Publishing as Benjamin Cummings
31 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 CH3—C—O—CH2—CH H2O ethyl acetate (an ester)
32 Learning Check Write the equation for the reaction of propanoic acid and methanol in the presence of an acid catalyst.
33 Solution 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 CH3—CH2—C—O—CH H2O
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 O methyl CH3— O—C —CH3 ethanoate (acetate) IUPAC: methyl ethanoate common: 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.
36 Esters in Plants fruits their pleasant fragrances and flavors.
Esters give flowers and fruits their pleasant fragrances and flavors. TABLE 16.4 Copyright © 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 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)
39 Learning Check Name the following esters: O ║ A. CH3—CH2—CH2—C—O—CH3
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 CH3—CH2—CH2—C—O—CH2—CH2—CH3
43 Chapter 16 Carboxylic Acids and Esters
16.5 Properties of Esters Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
44 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—CH H2O H—C—OH + H—O—CH2—CH3
45 Base Hydrolysis (Saponification)
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—CH NaOH CH3—C—O– Na+ + HO—CH2—CH3 salt of carboxylic acid alcohol
46 “Soaps” The base hydrolysis of long chain fatty acids
produces acid salts called “soaps”. Copyright © by Pearson Education, Inc. Publishing as Benjamin Cummings
47 Cleaning Action of Soap
A 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 © by Pearson Education, Inc. Publishing as Benjamin Cummings
48 Learning Check A. Water and an acid catalyst B. KOH
Write the organic products when methyl acetate reacts with A. Water and an acid catalyst B. KOH
49 Solution A. Water and an acid catalyst O CH3—C—OH + HO—CH3 B. KOH
Write the organic products when methyl acetate reacts with: A. Water and an acid catalyst O CH3—C—OH HO—CH3 B. KOH CH3—C—O– K HO—CH3