Organic Chemistry Amines

1. AMINES
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Organic Chemistry
Class XII
Dr. Tanuja Nautiyal

2. Amines
 Amines are similar to ammonia (base) with one
or more alkyl groups bonded to the nitrogen
atom.
 Amines occurs widely in living organisms.
 Many amines are naturally occurring
compounds that are very active physiologically.
 Numerous drugs used for the treatment of
mental illness, hay fever, heart problems, and
other physical disorders are amines.

3. Bonding Characteristics of Nitrogen
Atoms in Organic Compounds:
 Carbon forms four bonds.
(4 valence electron, 4 covalent
bond, No nonbonding electron
pair).
Nitrogen forms three bonds
(5 valence electron, 3 covalent bond,
1 nonbonding electron pair).

4. An Amine is an organic derivative of ammonia
(NH4) in which one or more alkyl, cycloalkyl, or
aryl groups are attached to the nitrogen atom.
Alkyl amine
Aryl amine

5. Classification of Amines
Amines are classified on the basis of how many
hydrocarbon groups are bonded to the
ammonia nitrogen atom as:
 Primary amines (10)
 Secondary amines (20)
 Tertiary amines (30)

6. Classification of Amines
Primary Amine
Primary Amine is an amine in which the nitrogen atom is
bonded to one hydrocarbon group and two hydrogen
atoms.
The generalized formula for a primary amine is RNH2.
The functional group present in a primary amine, the NH2
group is called an Amino group.
An Amino group is the -NH2 functional group.
CH3 – NH2

7. Classification of Amines
Secondary Amine
Secondary Amine Is an amine in which the nitrogen
atom is bonded to two hydrocarbon groups and one
hydrogen atom. The generalized formula for a
secondary amine is R2NH. CH3 – NH – CH3

8. Classification of Amines
Tertiary Amine
Tertiary Amine is an amine in which the nitrogen
atom is bonded to three hydrocarbon groups and
no hydrogen atom. The generalized formula for a
tertiary amine is R3N

9. Classification of Amines

10. Physical Properties of Amines:
 The methylamines (mono-, di-, tri-) and ethylamine
are gases at room temperature , other amines are
liquid at room temperature.
 Amines are irritating to the skin, eyes, and mucous
membranes and are toxic by ingestion.
 Aromatic amines are generally toxic. Amines are
readily absorbed through the skin and affect both
the blood and the nervous system.

11. Boiling points of amines
The boiling points of amines are intermediate
between those of alkanes and alcohols of similar
molecular mass.
Amines are higher than alkane boiling point, because
hydrogen bonding is possible between amine
molecules but not between alkane molecules.
Intermolecular hydrogen bonding of amines involves
the hydrogen atoms and nitrogen atoms of the amino
group.

12. Boiling points of amines
Tertiary
Amines
Primary
Amines
Secondary
Amines
Boiling point Increases
Tertiary amines have lower boiling point than
primary and secondary amines because
intermolecular hydrogen bonding is not possible in
tertiary amines.
Secondary and tertiary amines have no hydrogen
atoms directly bonded to the nitrogen atom.

13. Why the boiling point of amines are lower than those of
corresponding alcohols?
The boiling point of amines are lower than those of
corresponding alcohols, because N – H bonds are weaker
than O – H bonds, as nitrogen is less electronegative than
oxygen.
The difference in hydrogen-bond strength :
O– H electronegativity differences (3.5) -(2.1) = 1.4
N– H electronegativity differences(3.0) - (2.1) = 0.9

14. Solubility of Amines
Amines with less than six carbon atoms are infinitely
soluble in water.
This solubility results from hydrogen bonding between
the amines and water as amine nitrogen atom has a
nonbonding electron pair that can form a hydrogen
bond with a hydrogen atom of water.

15. Basicity of Amines
Both amines and ammonia
produce basic aqueous solution

16. Basicity of Amines
Amines and Ammonia are weak bases. The weak-base
behaviour of amines and ammonia are due to its
acceptance of a proton (H+) from water to produce
ammonium ion and hydroxyl ion.
NH3 + H2O → NH4
+ + OH-Ammonia
Ammonium ion
CH3NH2 + H2O → CH3NH3
+ + OH-Methylamine
Methyl ammonium ion
Both amines and ammonia produce basic aqueous
solution

17. Nomenclature of Amines

18. Nomenclature of Amines

19. Nomenclature of Amines
Naming the positive ion that results from the
interaction of an amine with water is based on the
following two rules:
Rule 1: For alkylamine, the ending of the name of the
amine is changed from amine to ammonium ion
Examples: Ethylammonium ion
Rule 2: For aromatic amines, the final –e of the name of
the amine is replaced by –iumion
Examples: Anilinium ion

20. Preparation of Amines

21. Reduction of nitro compounds
Aromatic amines are normally prepared by reduction of
the corresponding aromatic nitro compound.
Aniline is prepared from nitrobenzene. Reducing agents:
Fe/H+, Sn/H+ or catalytic hydrogenation (example, H2/Pd
or Pt or Ni).

22. Reduction of amides
Amides yield primary amines on reduction by lithium
aluminum hydride, LiAlH4. The oxygen atom is
replaced by two hydrogen atoms, 2o and 3o amides
produce 2o and 3o amines, respectively.

23. Reduction of Nitriles
Nitriles can be reduced by strong reducing agent like H2
with catalyst (Ni) or LiAlH4 to yield primary amines.

24. Hoffmann degradation of amides
Hoffmann degradation of amides Heating the amides
with a mixture of bromine and KOH or NaOH. amides
will change to amines. is used to shorten the chain by
one carbon.

25. Reduction of halides with ammonia
The reaction of ammonia with an alkyl halide leads to
the formation of a primary amine.
The primary amine that is formed can also react with
the alkyl halide, which leads to a di-substituted
amine.(2o amine)

26. Chemical Reactions of
Amines

27. Alkylation of amines
Reaction of amines with an acid gives a
quarternary salts (an ammonium ion)

28. Reaction of Amines
Formation of amides
From acid chloride
From acid anhydride
From esters

29. Reaction with nitrous acid
Primary aliphatic and aromatic amines form
alkyldiazonium salts with nitrous acid.

30. Reaction with nitrous acid
We get many useful products from alkyldiazonium salts,
as it is an unstable salt.

31. Reaction of nitrous acid with amines
Reaction of nitrous acid with aliphatic amines in cold
acidic solution can be used to distinguish between
primary, secondary and tertiary amines.
Primary amines
Secondary amines
Ternary amines

32. Reaction with nitrous acid
Secondary aliphatic and aromatic amines form
nitrosoamine (yellow oils) with nitrous acid.

33. Carbyl amine Reaction
Primary amines heated with tri-chloromethane and
alcoholic KOH solution will produce a foul odour
of isocyanide RNC

34. Conversion of Primary, Secondary & Tertiary Amines

35. Presentation by
Dr. Tanuja Nautiyal
Sharda Public School
Almora