Preparation of p-bromoaniline 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: 1
Preparation of p-bromo aniline from acetanilide
AIM:
To prepare p-bromo aniline from acetanilide.
PRINCIPLE:
Electrophilic aromatic substitution is an important class of organic
chemistry. Bromination of acetanilide provides a good example to study
orientation of the incoming electrophile on a moderately activated
aromatic nucleus. 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. Hence, bromination of acetanilide yields para substituted
product as major product and ortho as minor product.
CHEMICALS REQUIRED:
Acetanilide, KBrO3, KBr, tartaric acid, HCl.
APPARATUS:
Conical flask, Thermometer, Beaker, Funnel, Measuring cylinder,
reflux condenser, Filter paper.

3. SPP-1.8 (1.4A) Practical Organic Chemistry
DOS & R in Organic Chemistry, TUT Page 3
PROCEDURE:
Step-1: Preparation of p-bromoacetanilide
• A mixture of acetanilide, potassium bromate and potassium
bromide (1:1:1 molar ratio) is placed in a conical flask fitted with a
cork. The required volume of water (10 ml) was added and the
mixture is gently stirred on a magnetic stirrer.
• An aqueous solution of tartaric acid (0.01 mol in 10 ml of water) is
added in small portions over a period of 15 minutes. The reaction
mixture acquires a distinct yellow colour due to slight excess of
bromine, indicating that no more bromine is required for the
reaction.
• To ensure completion of bromination, the reaction mixture is
stirred for another 15 minutes and the crude product is filtered.
Step-2: Hydrolysis of p-bromoacetanilide
• Place 2 g of p-bromoacetanilide in 1oo mL round bottom flask /
conical flask fitted with reflux condesor.
• Add 20 mL of water and 5 mL of conc. HCl and reflux the
resulting reaction mixture for 30 minutes on water bath.
• Completion of reaction is indicates by dissolution of p-
bromoacetanilide. Cool the reaction mixture to lab temperature
and pour it into cold water.
• Adjust the pH of the resulting mixture to basic by addition of
saturated solution of Na2CO3 (pH 7-8), p-bromoaniline separates
out upon cooling.
• Collect the solid by filtration and dried. Weigh the product,
calculate the yield and obtain melting point.

4. SPP-1.8 (1.4A) Practical Organic Chemistry
DOS & R in Organic Chemistry, TUT Page 4
REACTION:
5 KBr KBrO3 6 Tartaric acid 3 Br2 3 H2O 6 Tartaric acid salt
HN
Br
O
NH2
Br
2. Na2CO3
1. HCl, H2O
HN
O
KBrO3, KBr
Tartaric acid
CALCULATIONS:
Compound Amount
Molecular
Weight
Moles Equivalent
Acetanilide 1 g
93.13
1.02 g/cm3 0.018 1
KBrO3 10.6 g 118.71 0.089 5
KBr 15 g - - -
Tartaric acid 1.2 g
THEORETICAL CALCULATION:
Step-1: Preparation of p-bromoacetanilide
135 g of Acetanilide gives 214 g of p-bromoacetanilide
1 g of Acetanilide will forms X g of p-bromoacetanilide
Theoretical yield =
Practical yield =

5. SPP-1.8 (1.4A) Practical Organic Chemistry
DOS & R in Organic Chemistry, TUT Page 5
Step-2: Hydrolysis of p-bromoacetanilide
214 g of p-bromoacetanilide gives 172 g of p-bromoaniline
2 g of p-bromoacetanilide will forms X g of p-bromoaniline
Theoretical yield =
Practical yield =
% Yield = (Practical yield) / (Theoretical yield) X 100
MECHANISM:
Preparation of p-bromoacetanilide
Step-1: Generation of Electrophile
5 KBr KBrO3 6 Tartaric acid 3 Br2 3 H2O 6 Tartaric acid salt
Step-2: Attack on Electrophile
HN
Br Br
HN
Br
H
HN
Br Br
HN
H
Br
Ortho-substituion
Para-substituion
O O
O O

6. SPP-1.8 (1.4A) Practical Organic Chemistry
DOS & R in Organic Chemistry, TUT Page 6
Step-2: Loss of proton and formation of product
HN
Br Br
HN
H
Br Br
HN
Br
-HBr
O O
O
Hydrolysis of p-bromoacetanilide
HN
Br
O O
H
H
H
HN
Br
OH
H2O
HN
Br
OH
OH
NH3
Br
-CH3COOH
Cl
NH2
Br
Na2CO3

7. SPP-1.8 (1.4A) Practical Organic Chemistry
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CHEMICAL TESTS:
Beilstein test
Acetanilice: No green flame with copper wire (-Ve)
p-bromoacetanilide: Green flame with copper wire (+Ve)
Solubility test
p-bromooacetanilide: Insoluble with HCl (-Ve)
p-bromoaniline: Soluble with HCl (+Ve)
Diazotization Reaction
p-bromooacetanilide: No Red dye formation with β-naphthol (-Ve)
p-bromoaniline: Red dye formation with β-naphthol (+Ve)
REPORT:
Structure and
name of the
compound
Theoretical
yield
Practical
yield
Percentage
yield
Theoretical
Melting
point
Experimental
Melting
point
NH2
Br
p-bromoaniline
60-64oC

8. SPP-1.8 (1.4A) Practical Organic Chemistry
DOS & R in Organic Chemistry, TUT Page 8
REFERENCES:
1. https://labmonk.com/synthesis-of-2-4-6-tribromoaniline-from-
aniline.
2. Resonance, March 2013, 282-284.