2. INTRODUCTION
The functional group:
□ Amides are derived from carboxylic acids.
□ A carboxylic acid contains the -COOH group, and
in an amide the -OH part of that group is replaced
by an -NH2 group.
3. □Primary amides are named by changing the
name of the acid by dropping the -oic acid or
-ic acid endings and adding -amide.
Nomenclature of amides
4. □ Secondary amides are named by using an
upper case N to designate that the alkyl group
is on the nitrogen atom.
□ Tertiary amides are named in the same way.
Nomenclature of amides
7. Preparation of Amides
□ Carboxylic acids
The carboxylic acid is first converted into an ammonium
salt which then produces an amide on heating.
The ammonium salt is formed by adding solid ammonium
carbonate to an excess of the acid.
■ For example, ammonium ethanoate is made by adding
ammonium carbonate to an excess of ethanoic acid.
■ When the reaction is complete, the mixture is heated and the
ammonium salt dehydrates producing ethanamide.
8. Preparation of Amides
□ Acid chlorides
In the first stage, the ammonia reacts with the
ethanoyl chloride to give ethanamide and hydrogen
chloride gas.
Then the hydrogen chloride produced reacts with
excess ammonia to give ammonium chloride.
…and you can combine both equation to give one
overall equation:
9. Reactions of amides
1. Hydrolysis
2. With nitrous acid
3. Reduction
4. Hoffmann degradation
5. Dehydration
10. Reactions of amides
1. Hydrolysis
➢ Acidic
■Used: concentrated acid (HCl/H2SO4).
■Products:
■ammonium or ammonium salt and
carboxylic acid
■Example:
11. 1. Hydrolysis
➢ Acidic
➢ General equation:
Reactions of amides
C
O
R NH2
H3 O+ + HCl
reflux
C
O
R O H
Cl-
+ NH4
+
N
R'
H
C
O
R N
+
H3O+ reflux
C
O
R OH
+ H
R''
R''
R'
12. Reactions of amides
1. Hydrolysis
➢ Alkaline
■Used: concentrated sodium
hydroxide solution.
■Products: ammonia or an amine
and carboxylate salt
■Example:
13. Reactions of amides
1. Hydrolysis
➢ Alkaline
➢ General equation:
C
O
R NH2
+
OH- reflux
C
O
R O-
+
NH3
C
O
R + O H - reflux
C
O
R
O-
+ N H
N
R '
R ''
R '
R ''
14. Reactions of amides
➢
➢
2. With nitrous acid
Amides reacts with nitrous acid (HNO2) to give carboxylic acid
and N2 gas.
Nitrous acid (HNO2) is unstable and is prepared in situ by the
reaction of dilute HCl or dilute H2SO4with sodium nitrite in the
absence of heat.
NaNO2 (s) + HCl (aq) → NaCl (aq) + O=N-OH (aq)
nitrous acid
➢R-CONH2 + HNO2 R-COOH + N2(evolved)+H2O
15. 2. With nitrous acid
O
R C NH2 N2
O
R C OH
HNO2
EXAMPLE
O
CH3 C NH2
ethanamide
2
3
O
CH C OH N
HNO2
amide carboxylic acid
ethanoic acid
Reactions of amides
16. Reactions of amides
3. Reduction
Amides, RCONR'2, can be reduced to the amine,
RCH2
NR'2 by conversion of the C=O to -CH2
-
Amides can be reduced by LiAlH4 but NOT the
less reactive NaBH4
17. Reactions of amides
➢
3. Reduction
Look at the N substituent in the following examples
(those bonds don't change!)
18. Reactions of amides
4. Hoffmann degradation
Hofmann degradation is a reaction between an
amide and a mixture of bromine and sodium
hydroxide solution. Heat is needed.
The net effect of the reaction is a loss of the -CO-
part of the amide group. You get a primary amine
with one less carbon atom than the original amide
had.
The general equation:
∆
19. 4. Hoffmann degradation
Example:
■Ethanamide methylamine
■full equation for the reaction is:
■The Hofmann degradation is used as a way
of cutting a single carbon atom out of a chain.
Reactions of amides
20. Reactions of amides
5. Dehydration
Amides are dehydrated by heating a solid mixture of
the amide and phosphorus(V) oxide, P4O10/
phosphorus oxychloride, POCl3.
Water is removed from the amide group to leave a
nitrile group, -CN. The liquid nitrile is collected by
simple distillation.
For example, with ethanamide, you will get
ethanenitrile.
21. C H E M I C A L TESTS T O DIFFERENTIATE BETWEEN
C A R B O X Y L I C A C I D DERIVATIVES
ACYL CHLORIDE ESTER AMIDE
Water Vigorous. White
fumes (HCl)
liberated.
No reaction No reaction
Acid hydrolysis Vigorous,
RCOOH formed
Reversible,
produces RCOOH
and alcohol
Form RCOOH
and ammonium
salt
Base hydrolysis Vigorous, salt of
RCOOH form
Non reversible,
forms
carboxylate salt
and alcohol
Ammonia gas
liberated
Ammonia Forms amide Form amide No reaction
Reduction No reaction Forms two
alcohols
Forms amine
Hoffman
degradation
No reaction No reaction Forms amine
