1. Amides are derived from carboxylic acids by replacing the -OH group of the carboxylic acid with an -NH2 group. Primary amides are named by changing the acid name to the acid name amide. Secondary and tertiary amides use uppercase N to designate the alkyl group on nitrogen. 2. Amides can be prepared from carboxylic acids or acid chlorides. From acids, an ammonium salt is formed which dehydrates to the amide upon heating. From acid chlorides, the acid chloride reacts with ammonia. 3. Amides undergo hydrolysis to form carboxylic acids and ammonia/ammonium salts. They also react with nitro

1. ORGANIC
CHEMISTRY II
CHM301
AMIDES
NURUL’ AIN BINTI JAMION

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. Nomenclature of amides

Primary amides are named by changing the
name of the acid by dropping the -oic acid or
-ic acid endings and adding -amide.

4. Nomenclature of amides


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.

5. Nomenclature of amides

6. Preparation of Amides
Carboxylic acids
 Acid chlorides


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.
2.
3.
4.
5.
Hydrolysis
With nitrous acid
Reduction
Hoffmann degradation
Dehydration

10. Reactions of amides
1.
Hydrolysis

Acidic
 Used:
concentrated acid (HCl/ 2SO4).
H
 Products:
 ammonium or ammonium salt and
carboxylic acid
 Example:

11. Reactions of amides
1.
Hydrolysis
Acidic


General equation:
O
H3O+ + HCl
C
R
O
NH2
R
O
+
R
C
N
R'
R''
C
O
H3 O+
Cl-
reflux
+
reflux
R
C
OH
+ NH4+
OH
R'
N
R''
H
H

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
Hydrolysis
1.

Alkaline

General equation:
O
+
C
R
NH2
O
OH-
+
OH-
R''
+
reflux
R
N
R'
R'
O
C
C
NH3
O-
C
R
O
R
+
reflux
O-
NH
R''

14. Reactions of amides
With nitrous acid
2.
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 H2SO4 with 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. Reactions of amides
2.
With nitrous acid
O
R
C NH2
HNO2
amide
O
R
C OH
N2
carboxylic acid
EXAMPLE
O
CH3
C NH2
ethanamide
HNO2
O
CH3
C OH
ethanoic acid
N2

16. Reactions of amides
Reduction
3.


Amides, RCONR'2, can be reduced to the amine,
RCH2NR'2 by conversion of the C=O to -CH2Amides can be reduced by LiAlH4 but NOT the
less reactive NaBH4

17. Reactions of amides
Reduction
3.

Look at the N substituent in the following examples
(those bonds don't change!)

18. Reactions of amides
Hoffmann degradation
4.



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 -COpart of the amide group. You get a primary amine
with one less carbon atom than the original amide
had.
The general equation:
∆

19. Reactions of amides
Hoffmann degradation
4.

Example:
 Ethanamide  methylamine
 full
 The
equation for the reaction is:
Hofmann degradation is used as a way of
cutting a single carbon atom out of a chain.

20. Reactions of amides
Dehydration
5.

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. CHEMICAL TESTS TO DIFFERENTIATE BETWEEN
CARBOXYLIC ACID DERIVATIVES
ACYL CHLORIDE
ESTER
AMIDE
W
ater
Vigorous. W
hite
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