Procedures for the nitration of bromobenzene and methyl benzoate use a mixture o
ID: 486911 • Letter: P
Question
Procedures for the nitration of bromobenzene and methyl benzoate use a mixture of conc. nitric acid and conc. sulfuric acid to generate the required nitronium ion. What is the role of sulfric acid in this mixture? Students are advised to dispose of the 95% ethanol mother liquor from the recrystallization step in the nitration of bromobenzene in a waste bottle for halogented wastes while the same solvent used for the recrystallization step in the nitration of methyl benzoate is disposed of in a non-halogenated waste bottle. Explain this apparent contradiction. What is the role of the AICI_2 and FeBr_3 catalysts used in the procedures for Friedel-Crafts alkylation and aromatic halogenation reactions described in this experiment? Why is potassium bromate and not elemental bromine used as the source for bromine in the bromination experiments?Explanation / Answer
1. In the nitration of bromobenzene and methyl benzoate, mixture of nitric acid and sulfuric acid are used to generate nitronium ion. Sulfuric acid acts as catalyst and promote in the generation of nitronium ion.
2. Ethanol from recrystallization of nitration of bromobenzene is disposed in waste bottle for halogenated solvent because during the nitration of bromobenzene, side products are ortho and meta nitro bromobenzene (halogenated side products) which are more soluble in ethanol as compare to para bromobenzene. Ethanol from nitration of methyl benzoate s disposed in waste bottle for nonhalogenated solvent because side product is non halogented ones.
3. The role of AlCl3 and FeBr3 catalysts used in the procedures for Friedel Crafts alkylation and aromatic halogenation reactions are to make alkyl group and halogen group more electrophilic by coordination of Alumium and Iron with halogen of alkyl halide anad halo of halogen.
4. Potassium bromate is used in the bromination experiment instead of elemental bromine because potassium bromate is easy to handle which generate bromomium ion (Br+) as electrophile in presence of protic acid.
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