Kb NH3 OHRNH2 Kb Basicity constant defined as the concentration of product of ionized and unionized form of amine Generally greater the Kb value higher the basicity Greater the presence of ID: 935827
Download Presentation The PPT/PDF document "BASICITY OF AMINES : COMPARISION" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
BASICITY OF AMINES: COMPARISION
Kb= [NH3+] [OH-]/[R-NH2]
Kb= Basicity constant defined as the concentration of product of ionized and unionized form of amine
Generally greater the Kb value higher the basicity.
Greater the presence of
electron
releasing alky group higher the sharing of lone pair of electron present in nitrogen
Kb values and basicity
expressed in (gram per mole) :
1. Ammonia: NH3 =
1.8 ×10-5
2. Methyl amine: CH3NH2 =37
×
10-5
3. Dimethyl amine: (CH3)NH =
54
× 10-5
4. Trimethyl amine (CH3)3N
=6.7
×
10-5
Primary amine is stronger than ammonia (lone pair electron easily available in primary amine)
Here, secondary amine is stronger than primary amine
However, tertiary amine is weaker than both primary and secondary amine. This is due to the presence of three electron releasing alky group gives electron crowding.
Slide2QUALITATIVE TESTS FOR ALIPHATIC AMINES:
Reaction with nitrous acid (HNO2)
Primary amine=yellow color gas formation due to nitrogen gas (N2)
Secondary amine=yellow oily layer of due to the formation of N-
nitroso
diethyl amine
Tertiary amine=formation of soluble tri- ethyl ammonium nitrite but no visible reaction
Reaction with
benzene sulphonyl chloride (C6H5 SO2-Cl)
(HINSBERG REACTION)
1. Primary amine= ppt ( soluble in NaOH)
2. Secondary amine=ppt(insoluble
in
NaOH
3. Tertiary amine= do not give reaction
Slide3CARBYLAMINE TEST: WITH CHCl3+2KOH
Primary amine = gives
iso-cyanide R-NC [carbylamines]
(Also known as iso-nitrile)
Secondary and tertiary amines =do not gives reaction