chapter 18 amines and amides - cms - cerritos...

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Chapter 18 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 -e in 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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A. CH3—CH2—CH2—NH2

1-propylamine, 1-propanamine, 1°

CH3|

B. CH3—CH2—N—CH3

ethyldimethylamine,

N,N-dimethylethanamine, 3°

Solution

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Write a structural formula for

A. 2-pentanamine

B. N-methyl-1-butanamine

Learning Check

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A. 2-pentanamineNH2

|CH3—CH—CH2—CH2—CH3

B. N-methyl-1-butanamine

CH3—CH2—CH2—CH2—NH—CH3

Solution

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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. anilineNH2

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18.2

Properties of Amines



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Boiling Points of Amines,

Alcohols, and Alkanes

The 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:



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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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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18.4

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 –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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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 following

amides 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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