Download Chapter 1 Chemical Bonding and Chemical Structure

Chapter 23
The Chemistry of Amines
Amines
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skatole
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Classification of Amines
• Amines are organic derivatives of ammonia
• Note how amines are classified differently from that
of alcohols
23.1 Nomenclature of Amines
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Common Nomenclature
• For simple amines, add “amine” to the name of the
alkyl group
• When alkyl groups differ, name the amine as an Nsubstituted amine
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Common Nomenclature
• Aromatic amines are named as derivatives of
aniline
23.1 Nomenclature of Amines
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Substitutive Nomenclature
• Amines are named in a similar fashion to the their analogous
alcohols
– Remove the “-e” and replace it with “-amine”
• If there is more than one amino group, use Greek prefixes to
indicate how many and numbers to indicate location on the
alkyl chain
23.1 Nomenclature of Amines
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• When alkyl groups differ, use the Nsubstitution system
• When there is more than one substituted
amine, use N and N’ to differentiate
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• Name the amino group as a substituent when
there is a higher priority principal group
• Recall:
Substitutive Nomenclature
• Heterocyclic amines
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Problems
1) Name the following compounds:
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2) Draw the following molecules
• 2-propen-1-amine
• N-methyl-N’-propyl-1,4-butanediamine
• p-aminophenol
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Structure of Amines
• Bond length:
• Most amines undergo rapid inversion at N
23.2 Structure of Amines
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Physical Properties of Amines
• H-bonding ability increases boiling point
Diethylamine, MW = 71.1 amu
bp = 56.3°C
Pentane, MW = 72.1 amu
bp = 36.1°C
• Low molecular weight amines tend to be water soluble
whether they are primary, secondary or tertiary
• Fewer than 5 carbons usually = solubility in water
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Basicity of Amines
• Amines react with acids to form ammonium salts
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Separations Using Amine Basicity
• Ammonium salts are ionic compounds which imparts a high
degree of water-solubility
• This property can be useful in separation of amines from
other compounds
Acidity of Amines
• NH3, RNH2, and R2NH are amphoteric: they may act as bases
and acids
• They are very weakly acidic
– Will give up H+ to a very strong base
• The conjugate base of an amine is called an amide (do not
confuse with amide derivatives of carboxylic acids)
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Quaternary Salts
• Quaternary ammonium and phosphonium
salts are compounds in which all four groups
around the N and P are alkyl or aryl
23.6 Quaternary Ammonium and Phosphonium Salts
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Phase-Transfer Catalysis
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Synthesis of Amines
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Direct Alkylation of Amines
• Further alkylations can take place to give complex mixtures
Gabriel Synthesis of Primary Amines
• Direct alkylation is not a good method for the
preparation of primary amines
• The Gabriel synthesis allows for controlled
preparation
23.11 Synthesis of Amines
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• Hydrolysis of the phthalimide frees the amine
23.11 Synthesis of Amines
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Reduction of Nitro Compounds
• Catalytic hydrogenation:
• Reduction with finely divided metal powders:
23.11 Synthesis of Amines
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Reduction of Nitro Compounds
• LiAlH4 and NaBH4 fail to provide the amine
23.11 Synthesis of Amines
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Reductive Amination
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• Formaldehyde can be used to introduce methyl groups
• Neither an imine nor an enamine can be an intermediate in
the reaction of a secondary amine and formaldehyde
23.7 Alkylation and Acylation Reactions of Amines
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