This document discusses the properties and chemical behavior of aliphatic amines, highlighting their basicity compared to ammonia and the influence of structural variations on basicity levels. It provides specific pKb values for various amines and compares their solubility and solvent interactions. The document concludes that primary amines are generally stronger bases than secondary and tertiary amines and outlines factors affecting amine basicity.

1. ALIPHATIC AMINES

2. CONTENTS
PROPERTIES
FACTORS

3. Lower members
aliphatic amines ammonia smell
Higher members
fishy smell
physical sate
Boiling points
polar compounds Form molecular hydrogen bonding
Amines higherbioling points
N
H
R
H
H N H N H
R
H
R
H
Solubility
amines soluble in water
less in polar solvents
eg.organic solvents
H N
H
R
O
H
HH N
R
H

4. Chemical properties
Basicity of amine
R NH2 + HCl R NH Cl
3
+ -
1
0
amine
Salt
R NH2 + H2O R NH2OH R NH3 + OH
+
_
+ _
R NH2 + H2O R NH3 + OH
+ _
Kb =
(R NH3) (OH)
+
(RNH2)
pK
b
= -logKb
smaller value of pKb Stronger basicity of amine

5. pKb values
of amines
CH3NH2 3.36
CH3 CH2 NH2 3.25
(CH3)2 NH 3.28
(CH3)3 N 4.30
C6H5NH2 9.42
C6H5NHCH3 9.15
C6H5 N(CH3)2 8.95
(C6H5)2 NH 13.20
Compond pKb

6. (1)Aliphatic amines are stronger bases than ammonia
(2)Relatives Basicity of primary, secondary & tertiary amines
NH
3 R NH2
NH 3
R NH2
R NH R
1 amine 2 amine0
0
....
..
Ammonia
Ammonia
3
NH > CH NH > (CH ) N
323 3
(CH )2
secondary amine>primary amine>tertiary amine

7. Basis of factors
Inductive effect Solvation effect
3
NH > CH NH > (CH ) N
323 3
(CH )2
3
NH(CH )2(CH3)3 N > > CH3NH2
3 2 1
0 0 0
1
0
R NH2 > R2 NH > R3N
2 3
R2 NH > R NH2 > R2N
2 1 3
0 0
0 0 0
NH2
2 1
0 0
pKb=3.36 4.303.28
3
0
CH3)3N(CH3)2 NH CH3
ammonium ion from
primary amine
maximum solvation
secondary amine
ammonium ion from tetiary
amine
manimum solvation

8. Aromatic amines weak base aliphatic amines & ammonia
NH2:
I
NH2
+
-
NH2
+
-
NH2
+
-
NH2
II III IV V
+ H2O + OH
-
NH2NH2
+
anilinium ion
NH3 NH3
++

9. N Alkyl anilines are stronger bases than aniline
N
CH3
CH3
>
H
N CH3
> NH2
N,N-dimethylamine
pKb=8.95
N-Methylamine
9.15
aniline
9.42

10. LETS GO AHEAD & SEE AGAIN