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Preparation of 2,4,6 tribromoaniline
- 1. CPP-1.5 (1.1) Practical Organic Chemistry DOS & R in Organic Chemistry, TUT Page 1 Prepared By Dr. Krishnaswamy G Faculty DOS & R in Organic Chemistry Tumkur University Tumakuru
- 2. CPP-1.5 (1.1) Practical Organic Chemistry DOS & R in Organic Chemistry, TUT Page 2 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.
- 3. CPP-1.5 (1.1) Practical Organic Chemistry DOS & R in Organic Chemistry, TUT Page 3 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: NH2 NH2 BrBr Br 5 KBr KBrO3 6 Tartaric acid 3 Br2 3 H2O 6 Tartaric acid salt 3 Br2
- 4. CPP-1.5 (1.1) Practical Organic Chemistry DOS & R in Organic Chemistry, TUT Page 4 CALCULATIONS: Compound Amount Molecular Weight Moles Equivalent Aniline 1 g 93.13 1.02 g/cm3 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 KBr KBrO3 6 Tartaric acid 3 Br2 3 H2O 6 Tartaric acid salt
- 5. CPP-1.5 (1.1) Practical Organic Chemistry DOS & R in Organic Chemistry, TUT Page 5 Step-2: Attack on Electrophile NH2 Br Br NH2 Br H NH2 Br Br NH2 HBr Ortho-substituion Para-substituion Step-2: Loss of proton and formation of product NH2 Br Br NH2 Br H Br NH2 Br Br Br NH2 HBr Br Br NH2 Br Br Br Br NH2 Br Br Br H Br NH2 Br Br Br -HBr -HBr -HBr
- 6. CPP-1.5 (1.1) Practical Organic Chemistry DOS & R in Organic Chemistry, TUT Page 6 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 NH2 Br Br Br 2, 4, 6-Tribromoaniline 120oC REFERENCES: 1. https://labmonk.com/synthesis-of-2-4-6-tribromoaniline-from- aniline. 2. Resonance, March 2013, 282-284.
- 7. CPP-1.5 (1.1) Practical Organic Chemistry DOS & R in Organic Chemistry, TUT Page 7