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CHAPTER 10 AMINES
CHEM 240: Fall 2019
Prof. Greg Cook
cook.chem.ndsu.nodak.edu/chem240
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Amine Classes
• We use the same designation of primary, secondary, tertiary and quaternary to indicate the degree of amine substitution. note: different than alcohols.
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Aliphatic Amines
• nitrogen attached only to alkyl groups.
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Aromatic Amines
• nitrogen attached directly to an aromatic ring.
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Nitrogen Heterocycles
• nitrogen is part of a ring
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Naming Amines
• Replace the suffix (-e) with -amine
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More Amine Naming
• Amines generally are lower priority
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Secondary and Tertiary Amines
• Use N- to indicate a substituent is attached to the nitrogen.
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Quaternary Ammonium Salts
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Common names
• Aromatic amines
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Common names
• Alkylamines
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Physical Properties of Amines
• Amines can form hydrogen bonds but they are weaker than alcohols and water. They are generally bases.
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RN
HH
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Acid-Base Properties
• Amines are weak bases and aqueous solutions are basic.
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pKa and pKb of bases
• pKa of protonated amine
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• -for any acid/conjugate base base pair . . .
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pKa and pKb of bases
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Kb = Keq[H2O] = [CH3NH3+][OH-]
[CH3NH2]=
4.37 x 10-11 = pKb = 3.36
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pKa and pKb of bases
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pKa and pKb of bases
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Basicity of different amines
• Aromatic amines are weaker bases than aliphatic amines. Lone pair is delocalized in resonance.
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Reactions with Acids
• All amines react quantitatively with strong acids to make salts. Many are water soluble.
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Synthesis of Aromatic Amines
• Aromatic amines are made by the reduction of nitro compounds.
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Amines react as nucleophiles
• Amines readily participate as nucleophiles in SN2 substitution reactions.
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Amines react as nucleophiles
• Often it is difficult to stop reactions after one alkylation.
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