1 lecture 7: amines and amides 18.1 amines copyright © 2007 by pearson education, inc. publishing...

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Lecture 7: Amines and Amides

18.1

Amines

Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings

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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. A tertiary (3°) amine has three carbon groups.

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 Simple 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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In the IUPAC system, Amines are named as alkanamines. The ein the alkane name of the longest chain is

changed to amine. The chain is numbered to locate the amine group

and substituents. NH2

| CH3—CH2—NH2 CH3—CH—CH3

Ethanamine 2-Propanamine

IUPAC Names of Amines

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In a secondary or tertiary amine, The longest alkane chain is numbered. Each alkyl group bonded to the N atom is named as

a N-alkyl group HN—CH3

|CH3—CH2—CH2—NH—CH3 CH3—CH—CH2—CH3

3 2 1 1 2 3 4

N-Methyl-1-propanamine N-Methyl-2-butanamine

Naming Secondary and Tertiary Amines

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Give the common and IUPAC names, and classify as

primary, secondary, or tertiary:

A. CH3—CH2—CH2—NH2

CH3

|B. CH3—CH2—N—CH3

Learning Check

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Write a structural formula for

A. 2-pentanamine

B. N-methyl-1-butanamine

Learning Check

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Aromatic Amines

The amine of benzene is aniline. Alkyl groups on the N use the prefix N-and the alkyl

name.

Aniline 3-chloroaniline N-methylaniline

NH2

Cl

NH2 CH3NH

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Learning Check

Give a name for each:

A. CH3—NH—CH2—CH3

CH3

|

B. CH3—CH2—N—CH2—CH2—CH2—CH3

C. NH2

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Solution

A. CH3—NH—CH2—CH3

ethylmethylamine; N-methylethanamine

CH3

|B. CH3—CH2—N—CH2—CH2—CH2—CH3

N-ethyl-N-methyl-1-butanamine

C. aniline

NH2

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18.2

Properties of Amines


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Boiling Points of Amines, Alcohols, and AlkanesThe boiling points of amines are Higher than alkanes. Lower than alcohols of similar mass.

Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

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Hydrogen Bonding for Amines

The polar N-H bond Provides hydrogen bonding in 1°and 2° amines, but

not 3°. In amines is not as polar as the O-H bonds in

alcohols.


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Solubility in Water

Amines are soluble in water If they have 1-5 carbon atoms. Because the N atom in smaller amines forms

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(s) is(are) 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(s) is(are) soluble in water?1. CH3—CH2—CH2—NH2


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Amines are Bronsted-Lowry bases that attract a H+ from H2O

to the N atom. 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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Cocaine

Cocaine Is sold illegally as an amine salt. Is reacted with NaOH to produce the free amine form

known as “crack”.


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Learning Check

Write the equation for ethylamine when it reacts with

each of the following:

1. + H2O

2. + HCl

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Solution

Write the equation for ethylamine when it reacts with

each of the following:

1. CH3—CH2—NH2 + H2O CH3—CH2—NH3+ OH–

2. CH3—CH2—NH2 + HCl CH3—CH2—NH3+ Cl–

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18.3

Heterocyclic Amines and Alkaloids


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Heterocyclic Amines

A heterocyclic amine Is a cyclic organic compound. Has a five- or six-atom ring. Contains one or more nitrogen atoms.

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Examples of Heterocyclic Amines

N

NN

N

N

H

N

H

N

H

Pyrrolidine Pyrrole

Piperidine Pyridine Pyrimidine

N

N

N

N

H

Purine

N

H

Imidazole


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Learning Check

Identify the following heterocyclic amines:

1. 2. 3.

N

H

N

H

N

H

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Solution

Identify the following heterocyclic amines:

1. 2. 3.

1. piperidine 2. pyrrole 3. imidazole

N

H

N

H

N

H

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Alkaloids are Physiologically active nitrogen-containing

compounds. Produced by plants. Used as stimulants, anesthetics, and

antidepressants. Often habit forming.

Alkaloids

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Caffeine

Caffeine Is a stimulant of the

central nervous system. Is found in coffee

beans, tea, chocolate, and soft drinks.

Contains an imidazole ring.


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Nicotine

Nicotine Increases the adrenaline level in the blood. Causes addiction to tobacco. Contains a pyrrolidine ring.

N

CH3

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Alkaloids Related to Morphine

Alkaloids Such as morphine and codeine are produced by the

poppy. Have been used for centuries as painkillers. Such as heroin and codeine are modifications of

morphine.


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Morphine and Codeine


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Pharmacology

An area of research in pharmacology Is to design drugs such as procaine, lidocaine, and

demerol that retain some of the characteristics of alkaloids.

Is to modify the structures of cocaine and morphine to produce anesthesia, but without the addictive side effects.

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Pharmacology


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Learning Check

Identify the heterocyclic amine in serotonin.

serotonin

HO

N

H

CH2 CH2 NH2

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Solution

Identify the heterocyclic amine in serotonin.

pyrrole

N

HOCH2

H

CH2 NH2

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18.4

Amides



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Preparation of Amides

Amides are prepared 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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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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Amides are named as alkanamides. IUPAC replaces –oicacidendingwith –amide. Common names replace -icacid 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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Aromatic Amides

The amide of benzene is named benzamide.

C

O

NH2

Benzamide

C

O

NH CH3

N methylbenzamide -

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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. pentanamideO

CH3–CH2–CH2–CH2–C–NH2

B. N-methylbutyramide O

CH3–CH2–CH2–C–NH–CH3

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Classification of Amides

Amides are classified according to the number of carbon atoms bonded to the nitrogen atom.

O H || | CH3—C—N—H Primary (1°) amide

O H || | CH3—C—N—CH3 Secondary (2°) amide

O CH3 || | CH3 —C—N—CH3 Tertiary (3°) amide

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Give the common and IUPAC names for the followingamides and classify as primary, secondary, or tertiary:

O || A. CH3—CH2—CH2—C—NH2

O CH3 || |B. CH3—C—N—CH2—CH3

Learning Check

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O ||A. CH3—CH2—CH2—C—NH2

butryamide (common); butanamide (IUPAC) primary(1°) amide

O CH3 || | B. CH3—C—N—CH2—CH3

N-ethyl-N-methylacetamide (common);

N-ethyl-N-methylethanamide (IUPAC)

tertiary (3°) amide

Solution

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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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18.5

Hydrolysis of Amides



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Hydrolysis of Amides

Amides undergo

acid hydrolysis base hydrolysis

carboxylic acid salt of carboxylic acid

ammonium salt and an amine or ammonia

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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 equation for 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—N—CH2—CH3 + NaOH

N-ethylpropanamide

O CH3—CH2—C—O– Na+ + CH3—CH2—NH2

Solution

1 lecture 7: amines and amides 18.1 amines copyright © 2007 by pearson education, inc. publishing...

Documents

dimethylamine ch

tertiary amines

water amines

models of amines

aromatic amines

benjamin cummings slide

properties of amines

ethyldimethylamine slide