Transcript Hein and Arena - Imperial Valley College

Chapter 25 Amides and Amines:
Organic Nitrogen Compounds
Hein * Pattison * Arena * Best
Version 1.0
Jerry Poteat
Science Department
Georgia Perimeter College
1 ©
John Wiley and Sons, Inc.
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
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25.1 Amides: Nomenclature and
Physical Properties
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Amides are nonbasic (i.e. neutral) nitrogen-containing compounds.
Amides are produced when a carboxylic acid is heated in the
presence of ammonia.
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IUPAC Rules for Naming Amides
1. Name the longest continuous carbon chain containing the
amide group.
2. Drop –ioc from the corresponding carboxylic acid and add
the suffix –amide.
For example,
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IUPAC Rules for Naming Amides
3. Use a capital N as the prefix if the amide nitrogen atom has an
alkyl group as shown here.
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Some amides have common names as shown here and
in Table 25.1 in the next slide.
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The physical properties of amides are determined largely by
hydrogen bonding. Because of hydrogen bonding the melting points
and boiling points are higher and the low molar mass amides are
water-soluble.
Figure 25.1 Examples of hydrogen bonding between (a) an amide and water
and (b) between amide molecules.
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This table summarizes some of the physical properties
of amides.
Property
Description
Polarity
Polar
Solubility
Low molar mass amides are
soluble in water
M.P./B.P.
Both m.p. & b.p. are high due to
hydrogen bonding
Physical
State/Appearance
Colorless/odorless solids at
room temperature except
formamide.
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25.2 Chemical Properties
of Amides
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Hydrolysis of Amides
An important reaction of amides is hydrolysis. Amides undergo acidic
and basic hydrolysis producing a carboxylic acid or carboxylate salt.
Acidic Hydrolysis
Basic Hydrolysis
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25.3 Polyamides: Condensation
Polymers
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Polyamides
Polyamides are condensation polymers that contain repeating amide
linkages as shown here.
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Polyamides are either synthetic like Nylon-66 are biological like
the enzyme chymotrypsin.
Example of a biological polyamide
Example of a synthetic polyamide
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25.4 Urea
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Urea
Urea is a simple diamide that is excreted in urine. Urea is the
metabolite the body uses to excrete toxic ammonia. The structure of
urea is shown here.
Urea is a white solid that melts at 133 C. It is very soluble in water
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Urea
Commercial applications involving urea include fertilizer and the
synthesis of plastics and barbiturates.
An example of a synthesis using urea,
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25.5 Amines: Nomenclature
and Physical Properties
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Amines are basic nitrogen-containing compounds that are derivatives
of ammonia. Amines are classified as primary ( i.e. the nitrogen atom
has one carbon atom attached ), secondary ( i.e. the nitrogen atom has
two carbon atoms attached) and tertiary (i.e. the nitrogen atom has
three carbon atoms attached) as seen below in these structures.
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IUPAC Rules for Naming Amines
1. Name the longest continuous carbon chain containing the
amine group.
2. Drop –e from the corresponding alkane and add the suffix –
amine.
For example,
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IUPAC Rules for Naming Amines
3. Use a prefix with a capital N if the amine nitrogen atom has an
alkyl group as shown here.
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Some amines have common names as shown here.
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Heterocyclic Compounds
Heterocyclic compounds are ring compounds which have two or
more atoms in the ring that are different. O, N, and S are the most
common heteroatoms. Many nitrogen based heterocyclic compounds
like those shown below are found in DNA.
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This table summarizes some of the physical properties
of amines.
Property
Description
Polarity
Polar
Solubility
Amines with six carbons or less are
very soluble in water
M.P./B.P.
Both m.p. & b.p. are high due to
hydrogen bonding
Physical
State/Appearance
Methyl and ethylamine are gases
with strong ammonia-like odors,
others are liquids with strong fishy
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odors
Amines are responsible for the strong odors of decaying flesh which
are produced by bacterial decomposition. Two of these compounds
are actually diamines as shown here.
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25.6 Preparation of Amines
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Preparation of Amines
Amines are prepared by:
1. Alkylation of ammonia and amines
2. Reduction of amides
3. Reduction of nitriles
4. Reduction of aromatic nitro compounds
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Alkylation of Ammonia and Amines
Four successive alkylations of ammonia eventually yields a quaternary
ammonium salt.
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Reduction of Amides
Lithium aluminum hydride reduces an amide to an amine
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Reduction of Nitriles
Nitriles are reduced to amines using hydrogen gas and a metal
catalyst
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Reduction of Aromatic Nitro Compounds
Nitrobenzene is reduced to aniline which is a common aromatic
amine.
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25.7 Chemical Properties of
Amines
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Alkaline Properties of Amines
Amines produce hydroxide ions in water just like ammonia.
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Alkaline Properties of Amines
Amines are weak bases. For example, compare the pH of the
following amines with the pH of ammonia.
A 0.1M solution of NH3 (ammonia) has a pH of 11.1 while CH3NH2
is more basic at a pH of 11.8. However an aromatic amine like aniline
is less basic at a pH of 8.8.
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Alkaline Properties of Amines
Amines are much more basic than amides and the body uses this fact
to convert toxic ammonia into urea as shown here.
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Alkaline Properties of Amines
Amines also are a source of positive charges on biological molecules
under physiological conditions. Dopamine and serotonin are
typical examples of these amines.
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Salt Formation
Because amines are weak bases , they react with strong acids to form
ammonium salts.
Methylamine for example reacts with strong acid yielding the
methylammonium salt.
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Formation of Amides
Amides are produced when primary and secondary amines
react with acid chlorides
.
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25.8 Sources and Uses of
Selected Amines
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Many antibacterial agents include nitrogen containing compounds
such as those shown here.
Amines and amides are found in the B-complex vitamins B1 and B3.
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Alkaloids are a class of compounds derived from plants that show
biological activity. Procaine is an example of a local anesthetic.
An alkaloid like nicotine stimulates the nervous system while the
opium alkaloids like methadone and cocaine have morphine-like
activity ( i.e. sleep inducing and analgesic properties).
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Amphetamines are a class of compounds that stimulate the central
nervous system. Amphetamines like methamphetamine mimics the
action of epinephrine which produces a feeling of well-being and
increased alertness.
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Barbiturates are a class of compounds that depress the central
nervous system. These sedatives contain amide groups. An example
is pentobarbital.
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Other examples of drugs containing the amine/amide functional groups
include tranquilizers like Valium and antidepressants like Prozac.
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Chapter 25 Summary
Amides and amines are nitrogen-containing compounds.
Amides are nonbasic while amines are basic.
Amides are derivatives of RCOOH while amines are derivatives of
NH3.
Amides are odorless while amines tend to have strong disagreeable
odors.
Urea is a diamide that the body uses to excrete toxic ammonia.
Amides are prepared by heating RCOOH in the presence of
ammonia.
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Chapter 25 Summary
Amines are prepared by reducing amides, nitriles, and nitro
compounds with reducing agents like LiAlH4 and H2/Ni.
Polyamides are condensation polymers that are synthetic like
Nylon-66 or biological polymers like proteins.
Amides and amines are found in a wide variety of compounds to
include antibacterial agents, vitamins, and drugs.
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