Preparation of 4'-Bromoacetanilide from Acetanilide.
Principle: Aromatic compounds can be conveniently brominated by the use of brominating agent, which is normally a solution of bromine in acetic acid. Bromination of activated aromatic compounds usually give 2, 4, 6-tribromo derivatives while moderately activating group like anilide give preferably the para bromo product.
Reaction:
Procedure: Dissolve 0.5 g acetanilide in 0.6 ml glacial acetic acid and add 2.5 ml bromine solution in acetic acid (25% w/v). Shake the mixture for 1 h. After 1 h, pour the mixture on to crushed ice (20 g) with stirring. Filter the separated product and wash with cold water. Dry the product, record the practical yield and re-crystallize it.
Re-crystallization: Dissolve the crude product in minimum amount of ethyl alcohol in a beaker by heating on a water bath. Filter the hot solution and cool the filtrate. The crystals of the product separate out. Filter, dry and record the melting point and TLC (using toluene as a solvent).
