amides and amines: organic nitrogen...
TRANSCRIPT
Chapter Outline
Chapter 25
Introduction to General, Organic, and Biochemistry, 10e John Wiley & Sons, Inc
Morris Hein, Scott Pattison, and Susan Arena
Amides and Amines: Organic Nitrogen Compounds
Nylon is one of the materials used to give these colorful sails their strength and durability.
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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
Chapter 25 Summary
Course Outline
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Amides are neutral nitrogen-containing compounds. They are not acidic or basic (neutral) and exist as molecules both in aqueous solution and as pure substances.
These compounds contain carbonyl groups. The carbonyl
group is directly connected to a nitrogen atom.
Amides: Nomenclature and Physical Properties
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Amides are prepared when a carboxylic acid is heated in the presence of ammonia.
Amides: Nomenclature and Physical Properties
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Amides: Nomenclature and Physical Properties
Ammonium salts of carboxylic acids can also be converted to amides by heating.
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IUPAC Rules for Naming Amides 1. Name the longest continuous carbon chain containing the
amide group. The carbonyl carbon atom is the #1 carbon atom.
2. Drop –oic from the corresponding carboxylic acid and
add the suffix –amide.
Amides: Nomenclature and Physical Properties
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IUPAC names for amides are formed from the IUPAC names of carboxylic acids. Here are two examples.
Amides: Nomenclature and Physical Properties
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3. Use a capital N (italicized) as the prefix if alkyl groups or other groups are attached directly to the amide nitrogen atom.
Amides: Nomenclature and Physical Properties
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The common names for amides are formed from the common names of carboxylic acids.
Amides: Nomenclature and Physical Properties
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IUPAC and common names of some amides are on Table 25.1 on the next slide . . .
Amides: Nomenclature and Physical Properties
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Write formulas for N-methylpentanamide and N,N-diethyl-2-methylhexanamide.
Your Turn!
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Write formulas for N-methylpentanamide and N,N-diethyl-2-methylhexanamide.
Your Turn!
CH3CH2CH2CH2C
O
NHCH3
N-methylpentanamide
CH3CH2CH2CH2CHC
CH3
O
N(CH2CH3)2
N,N-diethyl-2-methylhexanamide
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Physical Properties of Amides The physical properties of amides are determined largely
by hydrogen bonding.
Amides: Nomenclature and Physical Properties
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High water solubility and high melting and boiling are the result of hydrogen bonding.
Amides: Nomenclature and Physical Properties
A table summarizing the physical properties of amides is on the following slide . . .
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Polarity Solubility M.P./B.P. Physical State/Appearance
Polar Low molar mass amides are soluble in water Both m.p. & b.p. are high due to hydrogen bonding Colorless/odorless solids at room temperature except formamide.
Property Description
Amides: Nomenclature and Physical Properties
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Acidic Hydrolysis
Basic Hydrolysis
An important reaction of amides is hydrolysis. Amides undergo acidic and basic hydrolysis producing a carboxylic acid or carboxylate salt.
Chemical Properties of Amides
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Write the equations for the acidic and basic hydrolysis of the following amide.
Your Turn!
CH3CH2CH2CH2C
O
NH2
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Write the equations for the acidic and basic hydrolysis of the following amide.
Your Turn!
CH3CH2CH2CH2C
O
NH2 + H2O + H+ CH3CH2CH2CH2C
O
OH + NH4+
CH3CH2CH2CH2C
O
NH2 + NaOH CH3CH2CH2CH2C
O
O- + NH3
Acidic hydrolysis
Basic hydrolysis
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Polyamides are condensation polymers that contain repeating amide linkages as shown here.
Polyamides: Condensation Polymers
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Polyamides are either synthetic like Nylon-66 or are biological like the protein chymotrypsin. The structure of chymotrypsin is shown below.
Polyamides: Condensation Polymers
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The structure of synthetic Nylon-66 is shown here.
Polyamides: Condensation Polymers
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Urea is a simple diamide that is excreted in urine. Urea is the metabolite the body uses to excrete toxic ammonia.
Urea is a white solid that melts at 133 °C. It is very soluble in water.
Urea
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Urea is a common commercial product. It is widely used in fertilizers to add nitrogen to the soil and as a starting material in the production of plastics and barbiturates like barbituric acid.
Urea
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Classification of Amines Amines are basic nitrogen-containing compounds that are
derivatives of ammonia. Amines are classified as: • Primary (the nitrogen atom has one hydrocarbon group
directly attached) • Secondary (the nitrogen atom has two hydrocarbon
groups directly attached) • Tertiary (the nitrogen atom has three hydrocarbon groups
directly attached).
Amines: Nomenclature and Physical Properties
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Examples of primary (1o), secondary (2o) and tertiary (3o) amines are shown here.
Amines: Nomenclature and Physical Properties
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Classify the following amines as 1o, 2o or 3o.
Your Turn!
NH2
CH3
NHCH3
CH3CH2CHCH3
N(CH3)2
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Classify the following amines as 1o, 2o or 3o.
Your Turn!
NH2
CH3
NHCH3
CH3CH2CHCH3
N(CH3)2
1O 3O 2O
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IUPAC Rules for Naming Amines
1. Name the longest continuous carbon chain containing the amine group. The carbon atom attached to the amine group is the #1 carbon atom.
2. Drop –e from the corresponding alkane and add the suffix –amine.
Amines: Nomenclature and Physical Properties
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Here are some examples of primary amines.
Amines: Nomenclature and Physical Properties
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3. Use a prefix with a capital N (italicized) if the amine nitrogen atom has an alkyl group or other group attached (2o and 3o amines).
Amines: Nomenclature and Physical Properties
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4. In naming diamines, the final -e of the alkane name is not omitted.
Amines: Nomenclature and Physical Properties
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Simple amines are most often referred to by their common names.
The common names for aliphatic amines are formed by
naming the alkyl group or groups attached to the nitrogen atom, followed by the ending –amine.
Amines: Nomenclature and Physical Properties
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The common names of some amines are shown here.
Amines: Nomenclature and Physical Properties
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The most important aromatic amine is aniline (C6H5NH2). Derivatives are named as substituted anilines.
Amines: Nomenclature and Physical Properties
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Amines: Nomenclature and Physical Properties
When a group is substituted for a hydrogen atom in the ring, the resulting ring substituted aniline is named as we have previously done with aromatic compounds.
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Give names for the following amines.
Your Turn!
CH3 N
CH2CH2CH3
CH2CH3
IUPAC and common namesCH3CH2CHCH2CH3
NH2
IUPAC name
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Give names for the following amines.
Your Turn!
CH3 N
CH2CH2CH3
CH2CH3
IUPAC: N-ethyl-N-methyl-1-propanamineCommon: ethylmethylpropylamine
CH3CH2CHCH2CH3
NH2
IUPAC name: 3-pentanamine
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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 common heteroatoms found in heterocyclic compounds.
Nitrogen-based heterocyclic compounds like those shown
on the next slide are found in DNA . . .
Amines: Nomenclature and Physical Properties
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Amines: Nomenclature and Physical Properties
Some heterocyclic amines.
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Amines: Nomenclature and Physical Properties
Physical Properties of Amines Amines are capable of hydrogen bonding with water. As a
result, the aliphatic amines with up to six carbons are quite soluble in water.
Methylamine and ethylamine are flammable gases with a
strong ammoniacal odor. Trimethylamine has a “fishy” odor.
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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.
Amines: Nomenclature and Physical Properties
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Amines are prepared by: 1. Alkylation of ammonia and amines 2. Reduction of amides 3. Reduction of nitriles 4. Reduction of aromatic nitro compounds
Preparation of Amines
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Alkylation of Ammonia and Amines Ammonia can be alkylated producing primary, secondary
and tertiary amines in successive reacctions.
Preparation of Amines
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Four successive alkylations of ammonia eventually yields a quaternary ammonium salt as seen in the last reaction.
Preparation of Amines
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Reduction of Amides Lithium aluminum hydride (LiAlH4) reduces amides to an
amines.
Preparation of Amines
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Reduction of Nitriles Nitriles are reduced to amines using hydrogen gas and a
metal catalyst.
Preparation of Amines
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Reduction of Aromatic Nitro Compounds Nitrobenzene is reduced to aniline which is a common
aromatic amine.
Preparation of Amines
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Write the structure of an amide and a nitrile that when reduced would form 2-methyl-1-butanamine.
Your Turn!
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Write the structure of an amide and a nitrile that when reduced would form 2-methyl-1-butanamine.
Your Turn!
CH3CH2CHC
CH3
O
NH2
reductionCH3CH2CHCH2
CH3
NH2
CH3CH2CHC
CH3
N reduction2-methyl-1-butanamine
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Chemical Properties of Amines
Alkaline Properties of Amines Amines resemble ammonia in their reactions. Amines are
bases, and like ammonia, produce OH- ions in water
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Chemical Properties of Amines
The ions formed in the reaction of amines with water are substituted ammonium ions.
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Amines are weak bases. Compare the pH of the following amines with the pH of ammonia.
• A 0.1M solution of NH3 has a pH of 11.1 • CH3NH2 is more basic at a pH of 11.8. • An aromatic amine like aniline is less basic at a pH of
8.8.
Chemical Properties of Amines
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Amines are much more basic than amides and the body uses this fact to convert toxic ammonia into urea as shown here.
Chemical Properties of Amines
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Amines also are a source of positive charges on biological molecules under physiological conditions. The neurotransmitters dopamine and serotonin are typical examples of these charged amines.
Chemical Properties of 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 corresponding methylammonium salt.
Chemical Properties of Amines
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Chemical Properties of Amines
Methylammonium chloride is a white crystalline solid made up of methylammonium ions, CH3NH3
+, and chloride ions, Cl-.
Many amines or amino compounds are more stable in the
form of the hydrochloride salt. When the free amine is wanted, the HCl is neutralized to liberate the free amine.
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Formation of Amides Amides are produced when primary and secondary amines
react with acid chlorides.
Chemical Properties of Amines
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Show the products of the following reaction.
Your Turn!
CH3CH2C
O
Cl + H2NCH2CH3
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Show the products of the following reaction.
Your Turn!
CH3CH2C
O
Cl + H2NCH2CH3 CH3CH2C
O
NCH2CH3 + HCl
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Sources and Uses of Selected Amines
Nitrogen compounds are found throughout the plant and animal kingdoms.
Amines, substituted amines, and amides occur in every
living cell. Many of these compounds have important physiological effects.
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Sources and Uses of Selected Amines
Biogenic amines are derived from amino acids and act as neurotransmitters and hormones in animals.
• GABA (γ-aminobutyric acid) slows nerve action and can
bring relaxation.
• Norepinephrine shown below affects our focus and concentration.
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Sources and Uses of Selected Amines
Biogenic amines that act as hormones include the “fight-or-flight” hormone epinephrine (also a catecholamine) as well as histamine, an important component in allergic reactions.
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Sources and Uses of Selected Amines
Amphetamines are designed to mimic the action of biogenic amines and act as stimulants. They are used to treat depression, narcolepsy, and obesity.
The most widely abused amphetamine is
methamphetamine, commonly called “speed.”
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Sources and Uses of Selected Amines
Barbiturates are another class of drugs that are amines. These drugs are classified as sedatives and depress the activity of brain cells.
An example is pentobarbital.
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Basic compounds that are derived from plants and show physiological activity are known as alkaloids. These substances are usually amines.
Nicotine, an alkaloid derived from tobacco leaves, acts to
stimulate the nervous system.
Sources and Uses of Selected Amines
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Sources and Uses of Selected Amines
Coffee beans and tea leaves contain caffeine, an alkaloid stimulant.
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Sources and Uses of Selected Amines
The opium alkaloids are often called opiates and include both compounds derived from the opium poppy and synthetic compounds that have morphine-like activity. These compounds are sleep-inducing and have analgesic properties.
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Sources and Uses of Selected Amines
These drugs are classified as narcotics because they produce physical addiction, and they are strictly regulated by federal law. An example is methadone.
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Sources and Uses of Selected Amines
Another common narcotic alkaloid, cocaine, is obtained from the leaves of the coca plant.
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Chapter 25 Summary
• Carboxylic acids react with ammonia to form salts. • Amides are neutral, nonionic compounds. The IUPAC
naming of amides follows a similar process to that used for other organic molecules.
• Strong intermolecular hydrogen bonding accounts for the amides’ high melting, boiling points and water solubility.
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Chapter 25 Summary
• Amide hydrolysis uses water to split an amide into a carboxylic acid portion and a nitrogen-containing portion.
• Polyamides form when a carboxylic acid from one monomer reacts with an amine from a second monomer.
• Urea is a simple diamide of the structure. Animals excrete nitrogen in the form of urea. Urea is also a valuable fertilizer and industrial chemical.
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Chapter 25 Summary
• An amine is a substituted ammonia molecule bonded to at least one alkyl or aryl group.
• Many simple amines are referred to by their common names. The most important aromatic amine is aniline.
• Heterocyclic compounds are ring structures where the atoms forming the ring are not all alike.
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Chapter 25 Summary
• Intermolecular hydrogen bonding accounts for the amines’ high water solubility.
• Alkylation of ammonia (with alkyl halides) will successively form primary, secondary, and tertiary amines.
• Reduction of several different nitrogen-containing compounds will form amines.
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Chapter 25 Summary
• Amines are bases. Amines react with strong acids to form salts.
• Primary and secondary amines react with acid chlorides to form amides.
• Proteins are polymers of amino acids linked by amide bonds.
• Biogenic amines are derived from amino acids and act as neurotransmitters and hormones in animals.
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Chapter 25 Summary
• Many powerful drugs act by changing the biochemistry of biogenic amines.
• Basic compounds that are derived from plants and show physiological activity are known as alkaloids.