1 chapter 14 carboxylic acids, esters, amines, and amides 14.1 carboxylic acids

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Chapter 14 Carboxylic Acids, Esters, Amines, and Amides

14.1 Carboxylic Acids

A poem by Ogden Nash

The ant has made himself illustrious

Through constant industry industrious

So what?

Would you be calm and placid

If you were full of formic acid?

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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.

hydroxyl group or CH3COOH

carbonyl group

Carboxylic Acids

CH3 C OH

O

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In the IUPAC names of carboxylic acids

• the -e in the alkane name is replaced with -oic acid.

CH4 Methane HCOOH Methanoic acid

CH3—CH3 Ethane CH3—COOH Ethanoic acid

• substituents are numbered from the carboxyl carbon 1.

IUPAC Names

CH3 CH CH2 C OH

CH3 O

4 3 2 1

3-methylbutanoic acid

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Names and Sources of Some Carboxylic Acids

Common Names for Acids

HCOOH Formic Formica (ant)

CH3COOH Acetic Acetum (sour)

CH3CH2COOH Propionic Pro (first) + Pion (fat)

CH3(CH2)2COOH Butyric Butyrum (butter)

CH3(CH2)3COOH Valeric Valere (strong)

CH3(CH2)4COOH Caproic Caper (goat)

CH3(CH2)5COOH Enanthic Vine (wine)

CH3(CH2)6COOH Caprylic Caper (goat)

http://en.wikipedia.org/wiki/Carboxylic_acid

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Common Carboxylic Acids

methanoic acid (formic acid)

ethanoic acid (acetic acid)

CH3 C OH

O

H C OH

O

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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.

Benzoic Acid

Para-Aminobenzoic Acid

3,4-Dichlorobenzoic Acid

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14.2 Properties of Carboxylic Acids


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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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Comparison of Boiling Points

Compound Molar Mass Boiling Point

58 49 °C

60 97 °C

60 118 °C

CH3 CH2 C H

O

CH3 CH2 CH2 OH

CH3 C OH

O

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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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Acidity of Carboxylic Acids

Carboxylic acids • are weak acids.• ionize in water to produce carboxylate ions

and hydronium ions.

CH3 C OH + H2O CH3 C O- + H3O+

O O

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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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14.3 Esters

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Esters

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

ester group

CH3 C O CH3

O

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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.

Ethyl acetate (an ester)

Esterification

CH3 C OH + H O CH2 CH3H+

O

CH3 C O CH2 CH3

O

+ H2O

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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)

IUPAC: methyl ethanoate

common: methyl acetate

CH3 O C CH3

O

Naming Esters

Esters are named• with the alkyl group of the alcohol,• and the salt (-ate) of the carboxylic acid

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From methanol (methyl alcohol)

From ethanoic acid (acetic acid)

Methyl ethanoate(methyl acetate)

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Esters in Plants

Esters give pleasant fragrances and flavors to many fruits and flowers.

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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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14.4 Amines

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Amines

Amines

• are derivatives of ammonia, NH3.

• contain N attached to one or more alkyl or aromatic groups.

NH2

CH3 NH2 CH3 NH

CH3

CH3 N

CH3

CH3

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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

N

Do You

Know What

?

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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 meta-chloroaniline

NH2

Cl

NH2 CH3NH

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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 1-6 carbon atoms are soluble in water.• form hydrogen bonds with the polar O-H bond in water.

Copyright © 2009 by Pearson Education, Inc.

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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.

Ephedrine hydrochlorideEphedrine HClSudafed

Diphenhydramine hydrochlorideDiphenhydramine HClBenadryl

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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 (from coca leaves ) is• sold illegally as the amine salt.• reacted with NaOH to produce the free

amine form known as “crack.”

Cocaine hydrochloride Cocaine (free base)

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Caffeine• is a stimulant of the

central nervous system. • is found in coffee beans,

tea, chocolate, and soft drinks.

Caffeine

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.

Morphine Codeine

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14.5 Amides


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

carboxylic acids.

Amides

CH3 C OH

O

CH3 C NH2

O

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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. Methanamide (IUPAC) Formamide (common)

Propanamide (IUPAC)

Propionamide (common)

Naming Amides

H C NH2

O

C NH2

O

CH2CH3

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An alkyl group bonded to the N atom is named as N-alkyl in front of the amide name.

N-methylethanamide (IUPAC)N-methylacetamide (common)

N-ethylpropanamide (IUPAC)N-ethylpropionamide (common)

Naming Amides with N Groups

C N

O

CH2CH3 CH2 CH3

H

C N

O

CH3 CH3

H

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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, NembutalTM and SeconalTM 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

1 chapter 14 carboxylic acids, esters, amines, and amides 14.1 carboxylic acids

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