Amines

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Amines
                                                 
                                                  
                   
A Nitrogen, containing a lone pair is the key
atom
Resembles Ammonia where one or more Hs Are
replaced by alkyl groups
The lone pair participates in the reactivity Of
amines
Amines are a core part of amino acids
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Amines (structure)
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A fourth group is attached to the nitrogen
atom Using the lone pair. This is known as a
quaternary Ammonium ion
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2-aminoethanol
2-aminopentane
TRIS buffer, used widely in biochemistry
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Other examples
2-dimethylaminoethanol
2-methylaminoethanol
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Amine Nomenclature (contd)
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Aromatic amines

• The NH2 functional group is an amino group, and
  when this group is a substituent, amino- is used
  as a prefix
• The presence of the amine group increases the
  reactivity of the aromatic ring

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Properties of amines Basicity

• Amines are electron pair donors
• Bronsted-Lowry bases or lewis bases

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• Difference of boiling pts., similar molecular
  weights, why ?
• H-bonding significantly affects b.p
• Amine b.p are generally lower than alcohols
• Soluble in water (upto 6 carbons)
• Gaseous amines smell like ammonia, liquid amines
  have a
• A characteristic fishy smell!!

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Will 3o amines have higher b.p than 1o amines ?
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Heterocyclic Nitrogen compounds
Heterocycles are common in many naturally derived
products
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Back to basicity of Amines

• Basicity depends on
• Availability of Lone pair of electrons
• - Is the protonated form of the amine
  water-soluble?
• - Substituent groups on the amine

Ions of compound Kb
Ammonia NH3 1.810-5 M
Methylamine CH3NH2 4.410-4 M
propylamine CH3CH2CH2NH2 4.710-4 M
2-propylamine (CH3)2CHNH2 5.310-4 M
diethylamine (CH3)2NH 9.610-4 M
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Quarternary ions
Note heterocyclic ammonium ions are named by
using ium instead of -e