Experiment
Aim:
To Synthesize 2, 4, 6-Tribromo Aniline from Aniline.
Requirements:
Apparatus required: Round Bottomed Flasks, Beakers, Conical Flasks, Water bath vessel, Reagent bottles, Funnel, Measuring cylinder, Pipette, Stirrer, etc.
Instruments required: Weighing balance, Melting point apparatus, Hot air oven, Magnetic
stirrer.
Chemicals required: Aniline, Glacial acetic acid, Bromine solution, Ethanol, Activated
charcoal.
Theory:
Principle:
Bromination reaction:
The bromination reaction is a very useful electrophillic aromatic substitution reaction because brominated arene rings can be used to undergo carbon-carbon bond-forming reactions to build up chemical structures (e.g., Grignard reaction). Traditionally, a solution of acetic acid and molecular bromine (Br2) has been used to brominate aromatic systems. This is a hazardous mixture to handle, so a novel "green" way of performing the same reaction was invent. This novel method includes the reaction of sodium hypochlorite (NaClO) under acidic
conditions with sodium bromide to generate molecular bromine. This is much safer than handling acidic solutions of Br2 since most of the bromine made is consumed immediately by the electrophillic aromatic substitution reaction.
The unsaturated organic compounds are readily converted in to saturated compounds when reacted with halogens (chlorine, bromine, iodine).The amino group activates the nucleus to such an extent that substitution takes place at the two ortho and one para position. Thus reaction with bromine gives 2, 4, 6-tribromoaniline.
Procedure:
Place 4.66gm (0.05 mol) of aniline is dissolved in glacial acetic acid (50ml) in a
100 ml round bottom flask equipped with a magnetic stirrer. The solution is cooled on an ice/water bath before a solution of bromine 8.0ml (0.155mol) in glacial acetic acid (30ml) is added drop wise from an addition funnel drop wise at such a rate that complete decolourization is achieve between each drop. Stirred the reaction mixture continuously with magnetic stirring during the addition. (Remove the flask from the ice/water bath if the acetic
acid solidifies, momentarily). When all the bromine is added the reaction mixture is stirred 10min. (check TLC) before it is poured into water (250ml) containing a pinch of sodium bisulphite (NaHSO3). The precipitate is filtered off and washed with water. The product is recrystallized from hot ethanol with a pinch of activated charcoal.
Calculation:
Aniline:
Molecular Formula = CoH7N
Molecular Weight = 93gm
2,4,6-tribromo aniline:
Molecular Formula = C6H4Br3N
Molecular Weight = 329.81gm
93gm of Aniline is equivalent to 329.81gm of 2,4,6-tribromo aniline
4.66gm of Aniline gives how much?
4.66 x 329.81 = 16.52gm
93-gm
Theoretical Yield = 16.52gm
Practical Yield =
Percentage Yield : Practical Yield x 100
Theoretical Yield
Result:
The percentage yield of 2, 4, 6-Tribromo Aniline was found to be_______%.
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