7. General methods of preparation of Amines
NO2 NH2
Sn + HCl
Or Fe + HCl
Reduction with iron scrap and hydrochloric acid is preferred
1. Reduction of nitro compounds
Nitro compounds are reduced to amines by passing
hydrogen gas in the presence of finely divided nickel, palladium or
platinum
NO2 NH2
H2 / Pd
1.
Ethanol
2.
8.
9.
10. 2. Ammonolysis
The process of cleavage of the C-X bond by ammonia
molecule is known as ammonolysis
..
+ R - X
NH3
Nucleophile
+ -
R - NH3X
Substituted
ammonium salt
General methods of preparation of Amines
11. 2 2
R NH 3
R N
RNH
1o 2o 3o
+ -
R4NX
Ǫuaternary
ammonium salt
RX
RX
RX
Ammonolysis has the disadvantage of yielding a mixture of primary,
secondary and tertiary amines and also a quaternary ammonium salt.
11
General methods of preparation of Amines
12. General methods of preparation of Amines
2 2
R NH 3
R N
RNH
1o 2o 3o
+ -
R4NX
Ǫuaternary
ammonium salt
RX
RX
RX
Ammonolysis has the disadvantage of yielding a mixture of primary,
secondary and tertiary amines and also a quaternary ammonium salt.
13. How the yield of primary amines can be increased in ammonolysis ?
14. Primary amine is obtained as a major product by taking large excess
ammonia.
The order of reactivity of halides with amines is RI > RBr > RCl
General methods of preparation of Amines
Limitations of ammonolysis
1. Ammonolysis of alkyl halides does not give single amine but gives
a mixture of primary, secondary and tertiary amines.
2. Ammonolysis is not suitable for preparing aryl amines because of
the low reactivity of aryl halides towards nucleophilic
substitutions.
Reactivity decreases
15. General methods of preparation of Amines
R - C ☰ N R - CH2 - NH2
3. Reduction of nitriles
Nitriles on reduction with lithium aluminium hydride (LiAlH4)
or catalytic hydrogenation produce primary amines
H2 / Ni
Na(Hg) / C2H5OH
16. General methods of preparation of Amines
R - C ☰ N R - CH2 - NH2
3. Reduction of nitriles
Nitriles on reduction with lithium aluminium hydride (LiAlH4)
or catalytic hydrogenation produce primary amines
H2 / Ni
Na(Hg) / C2H5OH
17. General methods of preparation of Amines
R - C ☰ N R - CH2 - NH2
3. Reduction of nitriles
Nitriles on reduction with lithium aluminium hydride (LiAlH4)
or catalytic hydrogenation produce primary amines
H2 / Ni
Na(Hg) / C2H5OH
18. General methods of preparation of Amines
4. Reduction of amides
The amides on reduction with lithium aluminium hydride yield
amines
R - C - NH2 R - CH2 - NH2
I. LiAlH4
II. H2O
O
II
19. 5) By Hoffmann's Bromamide Reaction.
Primary (1°) acid amides on reaction with Br2 in the presence of
alkalies at about 343 K give primary amines. It may be noted that
amine formed by this method has one carbon atom less than the
parent amide.
General methods of preparation of Amines
20. 5) By Hoffmann's Bromamide Reaction.
Primary (1°) acid amides on reaction with Br2 in the presence of
alkalies at about 343 K give primary amines. It may be noted that
amine formed by this method has one carbon atom less than the
parent amide.
General methods of preparation of Amines
21. R - NH2 + NaBr + 2H2O
O
II
R - C - NH2 + Br2 + 4NaOH
General methods of preparation of Amines
22. R - NH2 + NaBr + 2H2O
O
II
R - C - NH2 + Br2 + 4NaOH
General methods of preparation of Amines
23. 6) Gabriel phthalimide synthesis - this method is used to prepare
pure 1oaliphatic amine or 1o
General methods of preparation of Amines
26. It may be noted that
1. Gabriel Synthesis yield only 1° amines.
2. 2° and 3° amines cannot he prepared by Gabriel synthesis
3. Aniline cannot be prepared by Gabriel synthesis. It is
because of the fact that aryl halides do not undergo
nucleophilic substitution under ordinary conditions.
General methods of preparation of Amines
27.
28. How will you convert
1. Benzene into aniline
2. Benzene into N, N-dimethylaniline
3. Cl-(CH2)4-Cl into hexan- 1,6-diamine ?
29. How will you convert
1. Benzene into aniline
2. Benzene into N, N-dimethylaniline
3. Cl-(CH2)4-Cl into hexan- 1,6-diamine ?
30.
31.
32. 1. Ethanoic acid into methanamine
2. Hexanenitrile into 1-aminopentane
3. Methanol to ethanoic acid
4. Ethanoic acid into propanoic acid
5. Methanamine to ethanamine
6. Propanoic acid into ethanoic acid ?
33. 1. Ethanoic acid into methanamine
2. Hexanenitrile into 1-aminopentane
3. Methanol to ethanoic acid
4. Ethanoic acid into propanoic acid
5. Methanamine to ethanamine
6. Propanoic acid into ethanoic acid ?
