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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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