Preparation of p-nitroacetanilide from Acetanilide

Preparation of p-nitroacetanilide from Acetanilide

1. SPP-1.8 (1.4A) Practical Organic Chemistry

DOS & R in Organic Chemistry, TUT Page 1






Prepared by
Dr. Krishna swamy
Faculty
DOS & R in Organic Chemistry
Tumkur University

2. SPP-1.8 (1.4A) Practical Organic Chemistry

DOS & R in Organic Chemistry, TUT Page 2


Experiment No: 2
Preparation of p-nitro acetanilide from acetanilide

AIM:
To prepare p-nitro acetanilide from acetanilide.
PRINCIPLE:
The nitration of aniline is difficult to carry out with nitrating mixture
since amino group gets oxidized and also mixture of products will be
formed. Hence, the amino group is first protected by acylation to form
acetanilide which is then nitrated to get p-nitroacetanilide as a major
product and o-nitro acetanilide as a minor product because the
acetamido group is less powerful ortho and para directing group than
amino group due to electron withdrawing carbonyl group and also it
blocks the ortho position by steric hindrance. Recrystallization from
ethanol readily removes the more soluble ortho compound and the pure
crystal of p-nitro acetanilide is obtained.
CHEMICALS REQUIRED:
Acetanilide, conc. HNO
3, conc.H2SO4, CH3COOH, Ethanol.
APPARATUS:
Conical flask, Thermometer, Beaker, Funnel, Measuring cylinder,
Filter paper.

3. SPP-1.8 (1.4A) Practical Organic Chemistry

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PROCEDURE:
• Add 2.5 g of acetanilide into 100 mL beaker containing 3 mL of
glacial acetic acid and 2 mL of con.H
2SO4. Stir the mixture by the
use of glass rod. Cool the resulting mixture in ice bath.
• Place 1.5 mL conc.HNO
3 in a clean test tube and cool it in a
freezing mixture (ice + salt). Then carefully add 1.5 mL
conc.H
2SO4 drop by drop with constant stirring.
• Place the test tube in a freezing mixture and wit until the
temperature becomes less than 5
oC.
• To the cooled content in the beaker add nitrating mixture drop
wise with constant stirring. During the addition temperature of
the mixture should not rise above 10
oC.
• After complete addition remove the beaker from the freezing
mixture and allow it to stand for 30 minutes at lab temperature.
• Pour the reaction mixture into cold water taken in a beaker with
stirring. Crude nitro acetanilide separates out at once.
• Filter the crude product and wash thoroughly with cold water till
it is free of acid.
• Dissolve the crude product in about 20 mL of ethanol. Warm the
content to get clear solution.
• Filter while hot and cool the filtrate in ice, colorless crystals of p-
nitro acetanilide were obtained.
• Collect the crystals by filtration and wash with cold ethanol.
• After drying, weigh the product, calculate the yield and obtain
melting point.

4. SPP-1.8 (1.4A) Practical Organic Chemistry

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REACTION:
HN
NO
2
O
HN
O
Con.HNO
3
Con.H
2SO
4
HN
O
0-5
o
C
NO
2
(Major) (Minor)

CALCULATIONS:
Compound Amount
Molecular
Weight
Moles Equivalent
Acetanilide 2.5 g 135.1 0.018 1
HNO3 1.5 mL - - -
H2SO4
2 mL +
1.5 mL
- - -
CH3COOH 3 mL - - -
THEORETICAL CALCULATION:
135 g of Acetanilide gives 180.1 g of p-nitroacetanilide
2.5 g of Acetanilide will forms X g of p-nitroacetanilide
Theoretical yield =
Practical yield =
% Yield = (Practical yield) / (Theoretical yield) X 100

5. SPP-1.8 (1.4A) Practical Organic Chemistry

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MECHANISM:
Step-1: Generation of Electrophile
HNO
3
H
2SO
4
H
2NO
3 HSO
4
NO
2
-H
2O

Step-2: Attack on Electrophile
HN
N
O
HN
NO
2
H
HN
HN
HO
2N
Ortho-substituion
Para-substituion
O
O
O
O
O
N
O
O

6. SPP-1.8 (1.4A) Practical Organic Chemistry

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Step-2: Loss of proton and formation of product
HN
HN
HO
2N
O
O
N
O
O
HSO
4
HN
NO
2
O

CHEMICAL TESTS:
Reduction and Diazotization test
Acetanilide: Does not undergo reduction with Sn and no dye
formation (-Ve)
p-nitro acetanilide: Undergo reduction with Sn and dye formation
(+Ve)

7. SPP-1.8 (1.4A) Practical Organic Chemistry

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REPORT:
Structure and
name of the
compound
Theoretical
yield
Practical
yield
Percentage
yield
Theoretical
Melting
point
Experimental
Melting
point

HN
NO
2
O


p-nitro acetanilide








214
oC


REFERENCES:
1. https://www.learncbse.in/to-prepare-a-sample-of-p
nitroacetanilide-from-acetanilide/
2. https://labmonk.com/synthesis-of-p-nitroaniline-from-
acetanilide