1 Chapter 13 Carboxylic Acids, Esters, Amines, and Amides 13.1 Carboxylic Acids Copyright © 2005 by...

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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─COOHC.

OHC

O

Br

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Solution

A. CH3─CH2─COOH propanoic acid

CH3

|

B. CH3─CH─CH2─COOH 3-methylbutanoic acid

C. 3-bromobenzoic acid OHC

O

Br

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13.2 Properties of Carboxylic Acids

Chapter 13 Carboxylic Acids, Esters, Amines and Amides


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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

Write the equation for the reaction of propanoic acid with

A. water

B. KOH

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Solution

Write the equation for the reaction of propanoic acid with

A. waterCH3—CH2—COOH + H2O CH3—CH2—COO– + H3O+

B. KOH CH3—CH2—COOH + KOH CH3—CH2—COO– K+ + H2O

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13.3 Esters


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Esters

In an ester, the H in the carboxyl group is replacedwith 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.

Learning Check

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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

Solution

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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.

CH3

O

CO

OH

O

C

OH

CH3O

O

C

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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.


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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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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

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Draw the structure of the following compounds.

A. 3-bromobutanoic acid

B. ethyl propionoate

Learning Check

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Solution

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 withA. water and an acid catalyst.

B. KOH.

Learning Check

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Write the organic products when methyl acetate reacts withA. water and an acid catalyst.

O CH3—C—OH + HO—CH3

B. KOH. O

CH3—C—O– K+ + HO—CH3

Solution

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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

NH2

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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 asprimary, secondary, or tertiary.

A. CH3—CH2—CH2—NH2

CH3

|B. CH3—CH2—N—CH3

Learning Check

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A. CH3—CH2—CH2—NH2

propylamine, 1°

CH3 |B. CH3—CH2—N—CH3

ethyldimethylamine, 3°

Solution

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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

NH2

Cl

NH2 CH3NH

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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

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Solution

A. CH3—NH—CH2—CH3 ethylmethylamine

CH3

|B. CH3—CH2—N—CH2—CH3

diethylmethylamine

C.

aniline

NH2

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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?

B. Which compound is soluble in water?

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Solution

Consider the following compounds.1) CH3—CH2—CH2—NH2


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


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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

CH3

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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

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Solution

A. methylpropylamine CH3–CH2–CH2–NH–CH3

B. 2-chloroaniline

NH2

Cl

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13.5 Amides



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

carboxylic acids. O O || ||

CH3—C—OH CH3—C—NH2

Amides


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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

O H │B. CH3–C–N–CH2–CH3

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Solution

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.

B. N-methylbutyramide.

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Solution

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.

Learning Check

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Write the products of the hydrolysis of

N-ethylpropanamide with NaOH.

O CH3—CH2—C—O– Na+ + CH3—CH2—NH2

Solution

1 Chapter 13 Carboxylic Acids, Esters, Amines, and Amides 13.1 Carboxylic Acids Copyright © 2005 by...

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