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Chapter 13 Carboxylic Acids,

Esters, Amines, and Amides

13.1

Carboxylic Acids

Copyright © 2005 by Pearson Education, Inc.

Publishing as Benjamin Cummings

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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.

O

CH3 — C—OH hydroxyl group or CH3COOH

carbonyl group

Carboxylic Acids

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Models of Carboxylic Acids

The three-dimensional models show the geometry of

atoms in carboxylic acid molecules.

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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

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Names and Sources of Some

Carboxylic Acids

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Common Carboxylic Acids

Methanoic acid (formic acid)

O

║

H─C─OH

ethanoic acid (acetic acid)

O

║

CH3─C─OH

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Aromatic Carboxylic Acids

Benzoic acid

• is the aromatic

carboxylic acid.

• locates substituents

by numbering the

ring from carbon 1 in

the carboxyl group.

OHC

O

OHC

O

OHC

O

ClNH2

3-chlorobenzoic acid 4-aminobenzoic acid

benzoic acid

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Learning Check

Give the IUPAC names of each compound.

A. CH3─CH2─COOH

CH3

|

B. CH3─CH─CH2─COOH

C.

OHC

O

Br

propanoic acid

3-methylbutanoic acid

3-bromobenzoic acid

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13.2 Properties of Carboxylic Acids

Chapter 13 Carboxylic Acids,

Esters, Amines and Amides

Copyright © 2005 by Pearson Education, Inc.

Publishing as Benjamin Cummings

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Polarity of Carboxylic Acids

Carboxylic acids

• are strongly polar.

• have two polar groups:

hydroxyl (−OH) and

carbonyl (C=O).

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Polarity of Carboxylic Acids

Carboxylic acids

• form dimers in which hydrogen bonds form between two carboxyl groups.

O H—O || | CH3—C C—CH3

| || O—H O

A dimer of acetic acid

• have higher boiling points than alcohols, ketones, and aldehydes of similar mass.

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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

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Solubility in Water

Carboxylic acids:

• form hydrogen bonds

with many water

molecules.

• with 1-4 carbon

atoms are very

soluble in water.

Water molecules

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Boiling Points and Solubility

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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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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.

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Learning Check

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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

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Chapter 13 Carboxylic Acids,

Esters, Amines, and Amides

13.3

Esters

Copyright © 2005 by Pearson Education, Inc.

Publishing as Benjamin Cummings

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Esters

In an ester, the H in the carboxyl group is replaced

with an alkyl group.

O

CH3 — C—O —CH3

ester group

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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

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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

Learning Check

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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.

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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.

methyl ethanoate (acetate)

O

CH3— O—C —CH3

IUPAC: methyl ethanoate

common: methyl acetate

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Esters in Plants

Esters give flowers and fruits their pleasant fragrances

and flavors.

Copyright © 2005 by Pearson Education, Inc.

Publishing as Benjamin Cummings

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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)

Learning Check

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Learning Check

Draw the structure of the following compounds.

A. 3-bromobutanoic acid

Br

|

CH3—CH—CH2—COOH

B. ethyl propionoate O

CH3—CH2 —C—O—CH2—CH3

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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

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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

Base Hydrolysis (Saponification)

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Base Hydrolysis of Fatty Acids

Produces Soaps

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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.

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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

Learning Check

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Chapter 13 Carboxylic Acids,

Ester, Amines, and Amides

13.4

Amines

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Amines

Amines

• are derivatives of ammonia, NH3.

• contain N attached to one or more alkyl or

aromatic groups.

CH3 CH3

CH3—NH2 CH3—NH CH3—N—CH3

N H 2

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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.

H CH3 CH3 | | | CH3—N—H CH3—N—H CH3—N—CH3

1° 2° 3°

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Models of Amines

The three-dimensional models show the shapes of amine molecules with one or more alkyl groups bonded to the nitrogen atom.

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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.

CH3—CH2—NH2 ethylamine

CH3—NH—CH3 dimethylamine

CH3

|

CH3—N—CH2—CH3 ethyldimethylamine

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Give the common name and classify as primary,

secondary, or tertiary.

A. CH3—CH2—CH2—NH2

CH3

|

B. CH3—CH2—N—CH3

Learning Check

propylamine, 1°

ethyldimethylamine, 3°

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Aromatic Amines

• The amine of benzene is named aniline.

• Alkyl groups on the N use the prefix N- with alkyl name.

aniline 3-chloroaniline N-methylaniline

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Learning Check

Give the common name of each compound.

A. CH3—NH—CH2—CH3

CH3

|

B. CH3—CH2—N—CH2—CH3

C. NH2

ethylmethylamine

diethylmethylamine

aniline

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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.

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Solubility in Water

Amines

• with 1-5 carbon atoms are soluble in water.

• form hydrogen bonds with the polar O-H bond in water.

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Learning Check

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?

1) CH3—CH2—CH2—NH2

B. Which compound is soluble in water?

1) CH3—CH2—CH2—NH2

2) CH3—CH2—NH—CH3

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Like ammonia, amines are weak bases in water.

NH3 + H2O NH4+ + OH–

ammonium hydroxide

CH3—NH2 + H2O CH3—NH3+ + OH–

methylammonium hydroxide

Amines React as Bases

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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—NH2 + HCl CH3—NH3+ Cl–

methylamine methylammonium

chloride

Neutralization forms Amine Salts

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Properties of Amine Salts

Amine salts are

• solids at room temperature.

• soluble in water and body fluids.

• the form used for drugs.

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Alkaloids

Alkaloids are

• physiologically active

nitrogen-containing

compounds.

• obtained from plants.

• used as anesthetics,

antidepressants, and in

stimulants such as

caffeine.

• often addictive.

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Cocaine

Cocaine is

• sold illegally as the amine salt.

• reacted with NaOH to produce the free amine form

known as “crack.”

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Caffeine

• is a stimulant of the central nervous system.

• is found in coffee beans, tea, chocolate, and soft drinks.

Caffeine

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Nicotine

Nicotine

• increases the adrenaline level in the blood.

• causes addiction to tobacco.

N

C H 3

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Morphine and Codeine

Morphine and codeine are

• alkaloids.

• obtained from the

oriental poppy plant.

• used as painkillers.

• modified to make heroin.

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Learning Check

Write the structural formula for

A methylpropylamine

B. 2-chloroaniline

CH3–CH2–CH2–NH–CH3

NH2

Cl

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13.5

Amides

Chapter 13 Carboxylic Acids,

Esters, Amines, and Amides

Copyright © 2005 by Pearson Education, Inc.

Publishing as Benjamin Cummings

53

In amides,

• an amino group(–NH2) replaces the –OH group of

carboxylic acids.

Amides

Copyright © 2005 by Pearson

Education, Inc.

Publishing as Benjamin

Cummings

O || CH3—C—OH

O || CH3—C—NH2

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Aromatic Amide

The aromatic amine is benzamide.

benzamide

O

CNH2

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Preparation of Amides

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

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Amides are named as alkanamides.

• IUPAC replaces –oic acid ending with –amide.

• Common names replace -ic acid ending with –amide.

O

Methanamide (IUPAC)

H—C—NH2 Formamide (common)

O Propanamide (IUPAC)

CH3—CH2—C—NH2 Propionamide (common)

Naming Amides

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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)

Naming Amides with N Groups

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Learning Check

Give the IUPAC and common names for the following:

O

A. CH3–CH2–CH2–C–NH2

butanamide; butryamide

O H

│

B. CH3–C–N–CH2–CH3

N-ethylethanamide; N-ethylacetamide

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Learning Check

Draw the structures of:

A. pentanamide

O

CH3–CH2–CH2–CH2–C–NH2

B. N-methylbutyramide

O

CH3–CH2–CH2–C–NH–CH3

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Some Amides in Health and

Medicine

• Urea is the end product of protein metabolism.

• Saccharin is an artificial sweetener.

• Some amides such as phenobarbital, Nembutal

and Seconal are barbiturates.

• Acetaminophen is used to reduce fever and pain.

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Some Amides in Health and

Medicine

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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 Hydrogen bonding occurs between primary amides. O || CH3—C—N—H | H

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Amides undergo

• Acid hydrolysis to produce a carboxylic acid and

an ammonium salt.

• Base hydrolysis to produce the salt of a carboxylic

acid and an amine or ammonia.

Hydrolysis of Amides

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acid hydrolysis O || O CH3—C—OH + NH4

+Cl– || HCl + H2O CH3—C—NH2

NaOH O || CH3—C—O– Na+ + NH3

base hydrolysis

Hydrolysis Reactions

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Write the products of the hydrolysis of

N-ethylpropanamide with NaOH.

O CH3—CH2—C—O– Na+ + CH3—CH2—NH2

Learning Check