This document discusses the properties and reactions of amines. It describes how amines are moderately polar and soluble in water due to hydrogen bonding. Their boiling points are higher than non-polar compounds due to intermolecular hydrogen bonding. Amines are basic due to the lone pair of electrons on nitrogen. Common reactions of amines include salt formation, alkylation, conversion to amides, aromatic substitution, Hofmann elimination, and formation of diazonium salts. Diazonium salts can undergo replacement or coupling reactions.

1. Amines
1

2. 2

3. 3

4. 4

5. 5

6. 6

7. 7

8. 8

9. 9

10. 10

11. 11

12. 12
Physical Properties of Amines
-Amines are moderately polar. For this reason the low formula
weight amines are readily soluble in water due to the formation
of hydrogen bonds with water.
-They have higher boiling points than non-polar compounds of the
same molecular weight, because of the formation of intermolecular
hydrogen bonds, except for tertiary amines.
)Intermolecular H bonds(
)H bonds with water(

13. 13

14. Physical Properties of Amines
14

15. Basicity of Amines
• The lone pair of electrons on nitrogen makes amines
basic and nucleophilic
• They react with acids to form acid–base salts and they
react with electrophiles
• Amines are stronger bases than alcohols, ethers, or
water

16. Amines as Bases
16

17. 17
High pKa → weaker acid and stronger conjugate base.

18. Aliphatic amines are stronger bases than aromatic amines because of
the resonance in aromatic amines
18

19. Electron-donating groups increase the basicity of amines,
Electron-withdrawing groups decrease the basicity of amines
CH3
CH2
NH2 CH2
(Cl)CH2
NH2
NH2
CH3
NH2
H
NH2
NO2
>>
is stronger base than
stronger base
19

20. 20
amines are stronger bases than amides
• Amides (RCONH2) in general are not proton acceptors except
in very strong acid
• The C=O group is strongly electron-withdrawing, making the
N a very weak base
• Addition of a proton occurs on O but this destroys the double
bond character of C=O as a requirement of stabilization by N

21. 21

22. 22
1-Reduction of Nitriles and Amides
Synthesis of Amines
CH2Br
NaCN
CH2C N
2 H2, Ni
CH2CH2NH2
benzyl bromide 1-amino-2-phenylethane

23. 23
2. Reduction of nitro compounds:

24. 24

25. CH3
HNO3,H2SO4
CH3
NO2
+ ortho-
H2,Ni
CH3
NH2
p-toluidine

26. 3- Ammonolysis of 1o
or methyl halides.
R-X
NH3 RNH2
R-X
R2NH
R-X
R3N
R-X
R4N+X-
1o 2o 3o
4o
salt
R-X must be 1o
or CH3
CH3CH2CH2CH2Br
NH3
CH3CH2CH2CH2NH2
n-butylamine

27. 27

28. 28

29. 4.Reductive amination:
O
H2, Ni
or NaBH3CN
CH NH2+ NH3
O
H2, Ni
or NaBH3CN
CH NHR+ RNH2
O
H2, Ni
or NaBH3CN
CH NR2+ R2NH
1o
amine
3o
amine
2o amine
• Ammonia, primary amines, and secondary amines yield
primary, secondary, and tertiary amines, respectively

30. Mechanism of Reductive Amination
• Imine is intermediate

31. H3C
C
O
CH3
acetone
NH3, H2/Ni
CH3CHCH3
NH2
isopropylamine
CCH2CH3
O
propiophenone
+ CH3CH2NH2
NaBH3CN
CHCH2CH3
NH
CH2CH3
1-(N-ethylamino)-1-phenylpropane
O
cyclohexanone
NH3, H2/Ni NH2
cyclohexylamine

32. 5. Hofmann degradation of amides
R C
NH2
O KOBr
R-NH2
Removes one carbon!
2,2-dimethylpropanamide
OBr
CH3C
CH3
CH3
NH2
tert-butylamine
CH3C
CH3
CH3
C
O
NH2

33. 33

34. 34
Reactions of Amines
- The lone-pair of electrons on the nitrogen atom dominates the
chemistry of the amines and cause them to function as Lewis
bases or nucleophiles
1- Basicity. Salt formation

35. NH2 + HCl NH3
+Cl-
(CH3CH2)2NH + CH3COOH (CH3CH2)2NH2
+
, -
OOCCH3
anilinium chloride
diethylammonium acetate

36. 2.Alkylation (ammonolysis of alkyl halides(
• Ammonia and other amines are good nucleophiles

37. CH3CH2CH2NH2
CH3Cl
CH3CH2CH2NHCH3
n-propylamine methyl-n-propylamine
NH2
2 CH3CH2Br
N
Et
Et
aniline N,N-diethylaniline
H2
C NH2
benzylamine
(xs) CH3I H2
C N
CH3
CH3
CH3 I
benzyltrimethylammonium iodide

38. 38
3- Conversion into amides
-Primary and secondary amines react readily with acid chlorides
and acid anhydrides to form N-substituted amides.

39. 39

40. 40

41. 41
-Tertiary amines do not possess a hydrogen atom bonded to
nitrogen and do not form amides with acid chlorides and acid
anhydrides.
Hinsberg Test:
unknown amine + benzenesulfonyl chloride, KOH (aq(
- Reacts to produce a clear solution and then gives a ppt upon
acidification  primary amine.
- Reacts to produce a ppt  secondary amine.
- Doesn’t react  tertiary amine.

42. 4- Ring substitution in aromatic amines
42
-Aromatic amines can undergo substitutions on the ring.
• The amino group forms a Lewis acid–base complex with the
AlCl3 catalyst, preventing further reaction
• -NH2, -NHR, -NR2 are powerful activating groups and
ortho/para directors
• -NHCOR less powerful activator than NH2

43. 43
NH2
+ Br2, aq.
NH2
Br Br
Br
no catalyst needed
use polar solvent
Br2,Fe
Br
HNO3
H2SO4
Br
NO2
+ ortho-
H2/Ni
Br
NH2
polyhalogenation!
NH2
CH3
+ CH3CH2Br, AlCl3
NR
Do not confuse the above with the alkylation reaction:
NH2
CH3
+ CH3CH2Br
NHCH2CH3
CH3

44. 44
5- Hofmann Elimination
• Converts amines into alkenes
• NH2
−
is very a poor leaving group so it converted to an
alkylammonium ion, which is a good leaving group

45. 45
6-Diazonium salts
i- Reactions of Diazonium Salts
1- Replacement of nitrogen
-Replacement of the diazonium group is the best general way of introducing
F, Cl, Br, I, CN, OH, and H into an aromatic ring.

46. 46
(a) Replacement by – Cl, - Br, - CN. Sandmeyer reaction

47. 47
(b) Replacement by – I
(c) Replacement by – F

48. 48
(d) Replacement by – OH
(e) Replacement by – H

49. 49
ii- Coupling
- Under the proper conditions, diazonium salts react with certain
aromatic compounds to yield products of the general formula
Ar – N = N – Ar', called azo compounds, this reaction, known
as coupling.

50. 50

51. of the following compounds Draw structures
51
a( Triethyl amine
b( 1,5-Pentanedi amine
c( N-Isopropyl-N-methyl cyclohexyl amine
d( N-Methyl
aniline