basic character of amjnes and amides

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