Download Lecture 7_Amines and Amides

Lecture 7: Amines and Amides
Amines
Amines
ƒ Are derivatives of ammonia NH3.
ƒ Contain N attached to one or more alkyl or aromatic
groups.
18.1
Amines
CH3—NH2
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CH3
⏐
CH3—NH
CH3
⏐
CH3—N—CH3
NH2
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Classification of Amines
Models of Amines
Amines are classified as primary, secondary, or tertiary.
ƒ In a primary (1°) amine, one carbon group is bonded
to the nitrogen atom.
ƒ A secondary (2°) amine has two carbon groups.
ƒ A tertiary (3°) amine has three carbon groups.
H
CH3
CH3
|
|
|
CH3—N—H
CH3—N—H
CH3—N—CH3
1°
2°
3°
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
IUPAC Names of Amines
Simple amines
ƒ Are named as alkylamines.
ƒ List the names of the alkyl groups bonded to the N
atom in alphabetical order in front of amine.
In the IUPAC system,
ƒ Amines are named as alkanamines.
ƒ The -e in the alkane name of the longest chain is
changed to -amine.
ƒ The chain is numbered to locate the amine group
and substituents.
NH2
|
CH3—CH—CH3
CH3—CH2—NH2
Ethanamine
2-Propanamine
CH3—CH2—NH2
ethylamine
CH3—NH—CH3
dimethylamine
CH3
|
CH3—N—CH2—CH3
ethyldimethylamine
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Naming Secondary and Tertiary
Amines
Learning Check
In a secondary or tertiary amine,
ƒ The longest alkane chain is numbered.
ƒ 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
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N-Methyl-1-propanamine
1
2
3
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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
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N-Methyl-2-butanamine
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Learning Check
Aromatic Amines
Write a structural formula for
A. 2-pentanamine
B.
ƒ The amine of benzene is aniline.
ƒ Alkyl groups on the N use the prefix N- and the alkyl
name.
NH2
N-methyl-1-butanamine
NH2
NH CH3
Cl
Aniline
3-chloroaniline
N-methylaniline
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Learning Check
Solution
Give a name for each:
A. CH3—NH—CH2—CH3
A.
B.
C.
CH3
|
CH3—CH2—N—CH2—CH2—CH2—CH3
CH3—NH—CH2—CH3
ethylmethylamine; N-methylethanamine
CH3
|
B. CH3—CH2—N—CH2—CH2—CH2—CH3
N-ethyl-N-methyl-1-butanamine
NH2
C.
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NH2
aniline
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Boiling Points of Amines,
Alcohols, and Alkanes
Lecture 7: Amines and Amides
The boiling points of amines are
ƒ Higher than alkanes.
ƒ Lower than alcohols of similar mass.
18.2
Properties of Amines
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Hydrogen Bonding for Amines
Solubility in Water
The polar N-H bond
ƒ Provides hydrogen bonding in 1°and 2° amines, but
not 3°.
ƒ In amines is not as polar as the O-H bonds in
alcohols.
Amines are soluble in water
ƒ If they have 1-5 carbon atoms.
ƒ Because the N atom in smaller amines forms
hydrogen bonds with the polar O-H bond in water.
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Learning Check
Solution
Consider the following compounds:
1. CH3—CH2—CH2—NH2
2. CH3—CH2—NH—CH3
3. CH3—CH2—CH2—CH3
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?
1. CH3—CH2—CH2—NH2
A. Which compound has the highest boiling point?
B. Which compound(s) is(are) soluble in water?
1. CH3—CH2—CH2—NH2
2. CH3—CH2—NH—CH3
B. Which compound(s) is(are) soluble in water?
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Amines React as Bases
Neutralization forms Amine Salts
NH4+ + OH–
An amine salt
ƒ Forms when an amine is
neutralized by acid.
ƒ Is named by replacing the amine
part of the name with ammonium
followed by the name of the
negative ion.
ammonium hydroxide
CH3—NH2 + HCl
CH3—NH3+Cl–
methylamine
methylammonium
chloride
Amines are
ƒ Bronsted-Lowry bases that attract a H+ from H2O
to the N atom.
ƒ Weak bases in water.
NH3 + H2O
CH3—NH2 + H2O
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CH3—NH3+ + OH–
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methylammonium hydroxide
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Properties of Amine Salts
Cocaine
Amine salts are
ƒ Solids at room temperature.
ƒ Soluble in water and body fluids.
ƒ The form used for drugs.
Cocaine
ƒ Is sold illegally as an amine salt.
ƒ Is reacted with NaOH to produce the free amine form
known as “crack”.
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Learning Check
Solution
Write the equation for ethylamine when it reacts with
each of the following:
Write the equation for ethylamine when it reacts with
each of the following:
1. + H2O
1. CH3—CH2—NH2 + H2O
CH3—CH2—NH3+ OH–
2. + HCl
2. CH3—CH2—NH2 + HCl
CH3—CH2—NH3+ Cl–
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Lecture 7: Amines and Amides
Heterocyclic Amines
18.3
Heterocyclic Amines and Alkaloids
A heterocyclic amine
ƒ Is a cyclic organic compound.
ƒ Has a five- or six-atom ring.
ƒ Contains one or more nitrogen atoms.
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Examples of Heterocyclic Amines
Learning Check
Identify the following heterocyclic amines:
N
N
H
Pyrrolidine
N
H
Pyrrole
H
Piperidine
N
1.
2.
3.
N
H
Imidazole
N
N
N
N
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N
N
N
N
N
H
H
H
N
H
Pyridine
Pyrimidine
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Purine
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Solution
Alkaloids
Identify the following heterocyclic amines:
1.
2.
N
N
N
H
H
H
1. piperidine
Alkaloids are
ƒ Physiologically active nitrogen-containing
compounds.
ƒ Produced by plants.
ƒ Used as stimulants, anesthetics, and
antidepressants.
ƒ Often habit forming.
3.
2. pyrrole
3. imidazole
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Caffeine
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Nicotine
Caffeine
ƒ Is a stimulant of the
central nervous system.
ƒ Is found in coffee
beans, tea, chocolate,
and soft drinks.
ƒ Contains an imidazole
ring.
Nicotine
ƒ Increases the adrenaline level in the blood.
ƒ Causes addiction to tobacco.
ƒ Contains a pyrrolidine ring.
N
CH3
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Alkaloids Related to Morphine
Morphine and Codeine
Alkaloids
ƒ Such as morphine and codeine are produced by the
poppy.
ƒ Have been used for centuries as painkillers.
ƒ Such as heroin and codeine are modifications of
morphine.
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Pharmacology
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Pharmacology
An area of research in pharmacology
ƒ Is to design drugs such as procaine, lidocaine, and
demerol that retain some of the characteristics of
alkaloids.
ƒ Is to modify the structures of cocaine and morphine
to produce anesthesia, but without the addictive
side effects.
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Learning Check
Solution
Identify the heterocyclic amine in serotonin.
Identify the heterocyclic amine in serotonin.
CH2
CH2 CH2 NH2
HO
HO
serotonin
CH2
NH2
pyrrole
N
N
H
H
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Lecture 7: Amines and Amides
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Preparation of Amides
Amides are prepared
ƒ By reacting a carboxylic acid with ammonia or
18.4
Amides
an amine (1° or 2°).
ƒ Using heat.
O
||
Heat
CH3—C—OH + NH3
O
||
CH3—C—NH2 + H2O
O
O
||
Heat
||
CH3—C—OH + CH3—NH2
CH3—C—NH—CH3 + H2O
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Amides
Naming Amides
In amides, an amino group(–NH2) replaces the –OH
group of carboxylic acids.
O
O
||
||
CH3—C—OH
CH3—C—NH2
Amides are named as alkanamides.
ƒ IUPAC replaces –oic acid ending with –amide.
ƒ Common names replace -ic acid ending with –amide.
O
||
Methanamide (IUPAC)
H—C—NH2
Formamide (common)
O
||
CH3—CH2—C—NH2
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Propanamide (IUPAC)
Propionamide (common)
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Naming Amides with N Groups
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Aromatic Amides
ƒ An alkyl group bonded to the N atom is named as
N-alkyl in front of the amide name.
O H
|| │
N-methylethanamide (IUPAC)
CH3 —C—N—CH3
N-methylacetamide (common)
O H
|| │
CH3—CH2 —C—N—CH2—CH3
N-ethylpropanamide (IUPAC)
N-ethylpropionamide (common)
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ƒ The amide of benzene is named benzamide.
O
O
C NH2
C NH CH3
Benzamide
N-methylbenzamide
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Learning Check
Solution
Give the IUPAC and common names for the following:
A.
O
||
CH3–CH2–CH2–C–NH2
B.
O H
|| │
CH3–C–N–CH2–CH3
A.
B.
O
||
CH3–CH2–CH2–C–NH2
butanamide; butryamide
OH
|| │
CH3–C–N–CH2–CH3
N-ethylethanamide; N-ethylacetamide
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Learning Check
Solution
Draw the structures of
A.
A.
pentanamide
B.
N-methylbutyramide
pentanamide
O
||
CH3–CH2–CH2–CH2–C–NH2
B.
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N-methylbutyramide
O
||
CH3–CH2–CH2–C–NH–CH3
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Classification of Amides
Learning Check
ƒ 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
O CH3
|| |
CH3 —C—N—CH3
Give the common and IUPAC names for the following
amides and classify as primary, secondary, or tertiary:
A.
O
||
CH3—CH2—CH2—C—NH2
B.
O CH3
|| |
CH3—C—N—CH2—CH3
Secondary (2°) amide
Tertiary (3°) amide
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Some Amides in Health and
Medicine
Solution
ƒ Urea is the end product of protein metabolism.
O
||
A. CH3—CH2—CH2—C—NH2
butryamide (common);
butanamide (IUPAC) primary(1°) amide
B.
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ƒ Saccharin is an artificial sweetener.
ƒ Some amides such as phenobarbital, Nembutal
and Seconal are barbiturates.
ƒ Acetaminophen is used to reduce fever and
pain.
O CH3
|| |
CH3—C—N—CH2—CH3
N-ethyl-N-methylacetamide (common);
N-ethyl-N-methylethanamide (IUPAC)
tertiary (3°) amide
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Physical Properties of Amides
Some Amides in Health and Medicine
Amides
ƒ That are primary (−NH2) or secondary (−NH−) form
hydrogen bonds.
ƒ That are primary have higher melting points than
secondary.
ƒ That are tertiary (no H on N) do not form hydrogen
bonds and have lower melting points.
ƒ All form hydrogen bonds with water.
ƒ With 1-5 carbon atoms are soluble in water.
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Hydrogen Bonding of Amides
O
||
CH3—C—N—H
|
H
O
||
CH3—C—N—H
|
H
Lecture 7: Amines and Amides
18.5
Hydrolysis of Amides
Hydrogen bonding occurs
between primary amides.
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Hydrolysis of Amides
Hydrolysis Reactions
acid hydrolysis
Amides undergo
acid hydrolysis
base hydrolysis
carboxylic acid
ammonium salt
salt of carboxylic acid
and an amine or ammonia
O
||
CH3—C—NH2
HCl + H2O
NaOH
O
||
CH3—C—OH + NH4+Cl–
O
||
CH3—C—O– Na+ + NH3
base hydrolysis
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Learning Check
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Solution
Write the equation for the hydrolysis of
N-ethylpropanamide with NaOH.
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
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