amines.pdf class xii Ncert CBSE aromatic and aliphatic amines

notes

1. Amines
Class XII

2. AMINES
•Amines are organic compounds that contain a
nitrogen atom bonded to one or more carbon atoms.
•They are incredibly versatile and play a crucial role in
various chemical reactions and biological processes.
•Amines play a vital role in biological systems. They
are found in essential biomolecules such as amino
acids, neurotransmitters, and hormones.
•The primary precursor for the synthesis of amines is
ammonia (NH
3). Through a process called amination,
ammonia can be reacted with organic compounds to
produce amines.

3. Types of amines

4. Roles of amines:
AGRICULTURE
MEDICINAL
CHEMISTRY
DYE INDUSTRIES
FOAMING AGENTS
FORENSICS
NEUROTRNSMITTERS
LUMINOL

5. Physical properties of amines
▪The lower aliphatic amines are gases with fishy odor, primary
amines with three or more carbon atom are liquid and the higher
ones are solid.
▪Aniline and other aryl amines are colorless but on storage develops
color due to atmospheric oxidation.
▪Lower aliphatic amines are soluble in water due to hydrogen bond
formation.
▪As the Molar mass of amines increases the solubility decreases.
(Due to increases in size of hydrophobic alkyl part)

6. Cont.
Order of solubility: 1° amine> 2° amine > 3° amine
Order of boiling point:1° amine> 2° amine > 3° amine
Order of volatility:3° amine >2° amine>1° amine
BOILING POINT: of 1° and 2° amines are lower than those
of alcohols of comparable molecular weight. The boiling
point of 3° amines which form no H–bonds are near to those
of alkanes of comparable molecular weight.
BOILING POINT∝ MOLECULAR WEIGHT

7. Chemical properties of amines
▪Basic character of amines is due to the presence of lone pair of electrons on the
N – atom and behave as nucleophiles.
▪Basic strength depends on electron donating tendency.
▪Order of basic character in aqueous solution :
Methy grp:
(CH
3)
2 NH [secondary]> CH
3NH
2[primary]> (CH
3)
3N [tertiary]> NH
3[ammonia]
Ethyl grp:
(C
2H
5)
2NH [secondary]> (C
2H
5)
3N[tertiary]> C
2H
5NH
2 [primary]> NH
3[ammonia]
•There is a subtle interplay of the inductive effect, solvation effect and
steric hinderance of the alkyl group which decides the basic strength of
alkyl amines in the aqueous state.

9. Basic character of amines
-Reacts with acids to form salts.
-Acts as Lewis base.
Chemical reactions of amines

11. Alkylation
-Reacts with alkyl halides to form higher amines.
-Acts as nucleophile.
-S
N2mechanism
Chemical reactions of amines
To understand
•Exhaustive
alkylation

12. Acylation
-Aliphatic and aromatic 1
o
and 2
o
amines undergo
acylation
-Acts as nucleophile.
-H is replaced by acyl groupto form amides.
-React withacid chlorides,anhydrides and esters.
-Reaction with benzoyl chloride (C
6H
5COCl) is called
benzoylation -(Schotten Baumann reaction)
Chemical reactions of amines

13. Acylation
Chemical reactions of amines

15. Carbylamine reaction
-Aliphatic and aromatic 1
o
amines undergo reaction
with CHCl
3 and ethanolic KOH/ NaOH
-Product: isocyanides /carbylamines (Foul smelling)
-Test for 1
o
amines (Qualitative)
-2
o
and 3
o
do not undergo the reaction
Chemical reactions of amines

17. Reaction with nitrous acid
-Nitrous acid: HNO
2 : prepared in situ(NaNO
2 + HCl)
-All amines react differently
-1
o
aliphatic amines→ diazonium salt→ N
2 + Alcohol
-1
o
aromatic amines→diazonium salt
-This process of conversion of primary amine to its
diazonium salt is known as diazotization.
Chemical reactions of amines

18. Chemical reactions of amines

20. Hofmann's mustard oil test
-Alkyl amine on treatment with CS2 and HgCl2
formalkyl isothiocyanate.
-Smelllike mustard oil
-Testfor 1
o
amine
-2
o
and 3
o
do not undergo the test
Chemical reactions of amines

21. Chemical reactions of amines
Hofmann's mustard oil test

22. Let's revise
➢Through a process called amination,ammonia
can be reacted with organic compounds
toproduce amines.
➢Types of amines: 1
o
, 2
o
, 3
o
and quaternary
➢Interplay of the inductive effect, solvation effect
andsteric hinderance of the alkyl group which
decides the basic strength ofalkyl amines in the
aqueous state.
➢Amines can act as nucleophiles (alkylation and
acylation) and Lewis bases(reaction with acid)

23. ➢Test to identify the types ofamines
Test 1
o
amine 2
o
amine 3
o
amine
Carbylamine test

Diazotization N2 gas Yellow oil Water soluble
product
Hofmann's
mustard oil test

24. Thank you!