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Chemistry Notes for class 12 Chapter 13
Amines
Amines constitute an important class of organic compounds derived by replacing one or more
hydrogen atoms ofNH 3 molecule by alkyl/aryl group(s).
In the IUPAC system, the amines are regarded as alkanamines, e.g.,
Structure
The nitrogen atom in amine is spa-hybridised. The three hybrid orbitals are involved in bond
formation and one hybrid atomic orbital contains the lone pair of electrons, giving the
pyramidal geometry of amines.
Methods of Preparation of Amines
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Ammonolysis has the disadvantage of yielding a mixture of primary, secondary and tertiary
amines and also a quaternary ammonium salt.
However, primary amine is obtained as a major product by taking large excess of NH3.
Order of reactivity of halides ‘with amines is RI > RBr > RCI.
Aromatic amines could not be prepared since aryl halides are much less reactive towards
nucleophilic substitution reactions.
(iii) Reduction of nitriles or cyanides
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(v) Reduction of amides
It only produces 1 0 amines. This method is not suitable for 1° arylamine because aryl halide
does not give nucleophilic substitution reaction.
(viii) Hofmann bromamide degradation reaction
In Hofmann degradation reaction, the amine formed has one carbon less than the parent amide.
To obtain primary amine with same number of carbon atoms from primary amide, reduction is
done with LiAlH4/ether.
Physical Properties of Amines
1. The lower aliphatic amines are gases with fishy smell.
2. Primary amines witb three or more carbon atoms are liquid and higher members are all
solids.
3. Lower aliphatic amines are water suluble because they can form hydrogen bonds with
water molecules, however the solubility decreases with increase in hydrophobic alkyl
group.
4. Boiling points order primary > secondary > tertiary
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Chemistry Notes for class 12 Chapter 13
Amines
Amines constitute an important class of organic compounds derived by replacing one or more
hydrogen atoms ofNH 3 molecule by alkyl/aryl group(s).
In the IUPAC system, the amines are regarded as alkanamines, e.g.,
Structure
The nitrogen atom in amine is spa-hybridised. The three hybrid orbitals are involved in bond
formation and one hybrid atomic orbital contains the lone pair of electrons, giving the
pyramidal geometry of amines.
Methods of Preparation of Amines
www.ncerthelp.com (Visit for all ncert solutions in text and videos, CBSE syllabus, note and many more)
,2|Page
Ammonolysis has the disadvantage of yielding a mixture of primary, secondary and tertiary
amines and also a quaternary ammonium salt.
However, primary amine is obtained as a major product by taking large excess of NH3.
Order of reactivity of halides ‘with amines is RI > RBr > RCI.
Aromatic amines could not be prepared since aryl halides are much less reactive towards
nucleophilic substitution reactions.
(iii) Reduction of nitriles or cyanides
www.ncerthelp.com (Visit for all ncert solutions in text and videos, CBSE syllabus, note and many more)
, 3|Page
(v) Reduction of amides
It only produces 1 0 amines. This method is not suitable for 1° arylamine because aryl halide
does not give nucleophilic substitution reaction.
(viii) Hofmann bromamide degradation reaction
In Hofmann degradation reaction, the amine formed has one carbon less than the parent amide.
To obtain primary amine with same number of carbon atoms from primary amide, reduction is
done with LiAlH4/ether.
Physical Properties of Amines
1. The lower aliphatic amines are gases with fishy smell.
2. Primary amines witb three or more carbon atoms are liquid and higher members are all
solids.
3. Lower aliphatic amines are water suluble because they can form hydrogen bonds with
water molecules, however the solubility decreases with increase in hydrophobic alkyl
group.
4. Boiling points order primary > secondary > tertiary
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