1

Amides and Amines: Organic Nitrogen Compounds

Chapter 25

Amides and Amines: Organic Nitrogen Compounds

Chapter 25

Hein * Best * Pattison * Arena

Colleen KelleyChemistry DepartmentPima Community College

© John Wiley and Sons, Inc.

Version 1.0

2

Chapter Outline

25.1 Amides: Nomenclature and Physical Properties

25.2 Chemical Properties of Amides

25.3 Polyamides: Condensation Polymers

25. 4 Urea

25.5 Amines: Nomenclature and Physical Properties

25.6 Preparation of Amines

25.7 Chemical Properties of Amines

25.8 Sources and Uses of Selected Amines

3

Nitrogen-Containing Compounds

• The amines and amides are the two major classes of nitrogen-containing compounds.

• Amines isolated from plants form a group of compounds called alkaloids.– Quinine, caffeine

• Amides are nitrogen derivatives of carboxylic acids.– Nylon, proteins

4

Amides: Nomenclature Amides: Nomenclature and Physical Propertiesand Physical Properties

5

• Carboxylic acids react with ammonia to form ammonium salts.

• When heated, ammonium salts of carboxylic acids lose a molecule of water and are converted to amides:

RC

OH

O

+ NH3

RC

O-NH4+

O

RC

NH2

O

+ H2O

carboxylicacid

ammonia

ammonium salt

amide

6

IUPAC Rules for Naming Amides

1. The IUPAC name is based on the longest carbon chain that includes the amide group.

2. Drop the –oic acid ending from the corresponding IUPAC acid name.

3. Add the suffix –amide.

7

Naming Amides

HC

NH2

O

methanamideH3C

CNH2

O

ethanamide

CNH2

O

benzamide

8

Naming Amides

• When the nitrogen of an amide is connected to an alkyl or aryl group, the group is named as a prefix preceded by the letter N:

H3CC

NHCH3

O

N-methylethanamide

9

10

Physical Properties of Amides• Except for formamide (methanamide), a

liquid, all other unsubstituted amides are solids at room temperature.

• Many are odorless and colorless.

• Low molar-mass amides are soluble in water, but solubility decreases quickly as molar-mass increases.

11

• The amide functional group is polar, and nitrogen is capable of hydrogen bonding.

12

Chemical Properties Chemical Properties of Amidesof Amides

13

Hydrolysis of Amides

H3CC

NH2

O

+ H2O + HCl H3CC

OH

O

+ NH4Cl

under acidic conditions:

H3CC

NH2

O

+ NaOH H3CC

O-Na+

O

+ NH3 (g)

under basic conditions:

14

Polyamides: Polyamides: Condensation Condensation

PolymersPolymers

Polyamides: Polyamides: Condensation Condensation

PolymersPolymers

15

Polyamides

• Polyamides are condensation polymers.

• Proteins are biological polyamides.

• Nylon-66 is a synthetic polyamide.

RC

OH

O

R'

H2C

NH

H

carboxylicacid group

amine groupR

C

O

R'

H2C

HN

+ H2O

amide linkage

16

UreaUrea

17

Urea• The body disposes of nitrogen by the

formation of a diamide known as urea.

• Urea is a white solid that melts at 133 C.

• It is soluble in water and therefore is excreted from the body in the urine.

H2NC

NH2

O

18

Amines: Nomenclature Amines: Nomenclature and Physical Propertiesand Physical Properties

19

H

NH H

ammonia

H

NH CH3

methylamineprimary amine

CH3

NH CH3

dimethylaminesecondary amine

CH3

NH3C CH3

trimethylaminetertiary amine

H

NH

cyclohexylamineprimary amine

H

NH

anilineprimary amine

20

IUPAC System for Naming Amines

1. The IUPAC system names simple amines by using the name of the alkane (omitting the final –e) and adding the ending –amine.

CH3CH2NH2 ethanamine

CH3CH2CH2NH2 1-propanamine

21

2. Secondary and tertiary amines are named as N-substituted primary amines by using the longest carbon chain as the parent name.

CH3

NH CH2CH2CH3

CH3

NCH3

N-methyl-1-propanamine

CH2CH3

NH3C CH2CH2CH2CH3

N-ethyl-N-methyl-1-butanamine

N,N-dimethylcylcohexanamine

22

Common Names of Amines

H

NH CH2CH2CH3

propylamine

H

NH CHCH3

CH3

isopropylamine

H

NH C

CH3

CH3

H3C

tert-butylamine

NH2

aniline

N(CH3)2

N,N-dimethylaniline

23

Heterocyclic Compounds• Ring compounds in which the atoms in the ring are not all alike are known as heterocyclic compounds.

•The most common heteroatoms are oxygen, nitrogen, and sulfur.

N

NNH

NHN

N

N

N

pyrrole pyridine pyrimidine purine

24

Physical Properties of Amines

• Amines are capable of hydrogen bonding with water.

• They have odors:

– Methylamine and ethylamine = strong ammoniacal odor

– Trimethyamine = ‘fishy’ odor

– High molar-mass amines = obnoxious odors

25

Preparation of Preparation of AminesAmines

Preparation of Preparation of AminesAmines

26

Preparation of Amines

1. Alkylation of ammonia and amines

2. Reduction of amides and nitriles

3. Reduction of aromatic nitro compounds

27

Alkylation of Ammonia and Amines

• The substitution of alkyl groups for hydrogen atoms of ammonia can be done by reacting ammonia with alkyl halides.

NH3+CH3Br CH3NH2+CH3Br (CH3)2NH

28

Reduction of Amides and Nitriles

H3CC

NH2

O

LiAlH4 CH3CH2NH2

CH3CH2CN CH3CH2CH2NH2H2/Ni

29

Reduction of Aromatic Nitro Compounds

NO2

SnHCl

NH3+Cl-

NaOH

NH2

30

Chemical Properties Chemical Properties of Aminesof Amines

31

Chemical Properties of Amines

1. Alkaline properties of amines

2. Salt formation

3. Formation of amides

32

Alkaline Properties of Amines

CH3NH2 + H-O-H CH3NH3 + OH-+

Amines are bases and produce OH- ions in water.

33

Salt Formation

• An amine reacts with a strong acid to form a salt.

CH3NH2 + H-Cl+

CH3NH3Cl-

34

Formation of Amides

• Primary and secondary amines react with acid chlorides to form substituted amides.

+ (CH3CH2)2NH2Cl-

H3CC

Cl

O

+ 2 (CH3CH2)2NH2 H3CC

N(CH2CH3)2

O

+

35