Preparation of 2,4,6 tribromoaniline

Preparation of tribromoaniline from aniline using potassium bromate, potassium bromide and tartaric acid

1. CPP-1.5 (1.1) Practical Organic Chemistry

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Prepared By
Dr. Krishnaswamy G
Faculty
DOS & R in Organic Chemistry
Tumkur University
Tumakuru

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Preparation of 2, 4, 6-tribromo aniline
AIM:
To prepare 2, 4, 6-tribromo aniline from aniline.
PRINCIPLE:
Electrophilic aromatic substitution is an important class of organic
chemistry. Substituents already present on benzene nucleus determine
the position and extent of substitution of the new incoming groups.
These substituents are generally classified as strongly activating (e.g. -
NH2), moderately activating (e.g.-NHCOCH3) and deactivating (e.g. -
NO2). Bromination of aniline provides a good example to study
orientation of the incoming electrophile on a strongly activated aromatic
nucleus. The amino group of aniline directs the electrophile to the two
ortho and one para position.
CHEMICALS REQUIRED:
Aniline, KBrO3, KBr, tartaric acid.
APPARATUS:
Conical flask, Thermometer, Beaker, Funnel, Measuring cylinder, Filter
paper.

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PROCEDURE:
 A mixture of potassium bromate and potassium bromide (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.
 Then aniline (1 mL) was added to the brominating mixture. 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.
 Weigh the product, calculate the yield and obtain melting point.
REACTION: NH
2
NH
2
BrBr
Br
5 KBrKBrO
36 Tartaric acid 3 Br
23 H
2O 6 Tartaric acid salt
3 Br
2

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CALCULATIONS:
Compound Amount
Molecular
Weight
Moles Equivalent
Aniline 1 g
93.13
1.02 g/cm
3

0.01 1
KBrO3 1.67 g 167 0.01 1
KBr 1.19 g 119 0.01 1
Tartaric acid 1.5 g 150.08 0.01 1
THEORETICAL CALCULATION:
93.13 g of Aniline gives 329.81 g of tribromoaniline
1 g of Aniline will forms X g of tribromoaniline
Theoretical yield =
Practical yield =
% Yield = (Practical yield) / (Theoretical yield) X 100
MECHANISM:
Step-1: Generation of electrophile 5 KBrKBrO
36 Tartaric acid 3 Br
2 3 H
2O 6 Tartaric acid salt

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Step-2: Attack on Electrophile NH
2
BrBr
NH
2
Br
H
NH
2
BrBr
NH
2
HBr
Ortho-substituion
Para-substituion

Step-2: Loss of proton and formation of product NH
2
BrBr
NH
2
Br
H
Br NH
2
BrBr
Br
NH
2
HBr Br
Br
NH
2
Br
Br
BrBr
NH
2
Br
Br
Br
H
Br
NH
2
Br
Br
Br
-HBr
-HBr
-HBr

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CHEMICAL TESTS:
Beilstein test
Aniline: No green flame with copper wire (-Ve)
Tribromoaniline: Green flame with copper wire (+Ve)
REPORT:
Structure and
name of the
compound
Theoretical
yield
Practical
yield
Percentage
yield
Theoretical
Melting
point
Experimental
Melting
point
NH
2
Br
Br
Br


2, 4, 6-Tribromoaniline

120
o
C


REFERENCES:
1. https://labmonk.com/synthesis-of-2-4-6-tribromoaniline-from-
aniline.
2. Resonance, March 2013, 282-284.

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