Basic character of amines PPT Chemistry Class 12

 Page 1


1
Page 2


1
objectives:
? Fundamental concepts on basic character of 
amines.
? Applications of these concepts in comparing the 
relative basic strengths of NH
3
, various alkyl 
amines, C
6
H
5
NH
2
and other substituted 
aromatic amines.
2
Page 3


1
objectives:
? Fundamental concepts on basic character of 
amines.
? Applications of these concepts in comparing the 
relative basic strengths of NH
3
, various alkyl 
amines, C
6
H
5
NH
2
and other substituted 
aromatic amines.
2
? Amines are derivatives of ammonia:
NH
3
R – NH
2
? Various types of amines are primary (1
0
), secondary (2
0
) and 
tertiary (3
0
):
RNH
2  
R
2
NH                        R
3
N
(1
0
)                        (2
0
)                          (3
0
)
? The basic nature of an amine is due to the presence of a lone 
pair on N, and its ability to donate it; and depends on the 
stability of the conjugate acid.
FUNDAMENTAL CONCEPTS ON 
BASIC CHARACTER OF AMINES
-H
+R
3
Page 4


1
objectives:
? Fundamental concepts on basic character of 
amines.
? Applications of these concepts in comparing the 
relative basic strengths of NH
3
, various alkyl 
amines, C
6
H
5
NH
2
and other substituted 
aromatic amines.
2
? Amines are derivatives of ammonia:
NH
3
R – NH
2
? Various types of amines are primary (1
0
), secondary (2
0
) and 
tertiary (3
0
):
RNH
2  
R
2
NH                        R
3
N
(1
0
)                        (2
0
)                          (3
0
)
? The basic nature of an amine is due to the presence of a lone 
pair on N, and its ability to donate it; and depends on the 
stability of the conjugate acid.
FUNDAMENTAL CONCEPTS ON 
BASIC CHARACTER OF AMINES
-H
+R
3
? Steric hindrance plays an important role in deciding basic 
strength.
? Electron releasing groups increase the basic strength , 
whereas electron withdrawing group decrease the basic 
strength of amines.
? A higher value of pK
b
implies lower basic strength.
4
Page 5


1
objectives:
? Fundamental concepts on basic character of 
amines.
? Applications of these concepts in comparing the 
relative basic strengths of NH
3
, various alkyl 
amines, C
6
H
5
NH
2
and other substituted 
aromatic amines.
2
? Amines are derivatives of ammonia:
NH
3
R – NH
2
? Various types of amines are primary (1
0
), secondary (2
0
) and 
tertiary (3
0
):
RNH
2  
R
2
NH                        R
3
N
(1
0
)                        (2
0
)                          (3
0
)
? The basic nature of an amine is due to the presence of a lone 
pair on N, and its ability to donate it; and depends on the 
stability of the conjugate acid.
FUNDAMENTAL CONCEPTS ON 
BASIC CHARACTER OF AMINES
-H
+R
3
? Steric hindrance plays an important role in deciding basic 
strength.
? Electron releasing groups increase the basic strength , 
whereas electron withdrawing group decrease the basic 
strength of amines.
? A higher value of pK
b
implies lower basic strength.
4
APPLICATION : COMPARISON 
OF NH
3
AND RNH
2
? As the alkyl group has +I – effect, it increases the 
electron density on N.
? Substituted ammonium ion is more stable due to 
charge dispersal by the alkyl group. 
So, RNH
2
is more basic than NH
3
.
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