In the nitration of bromobenzene that leads to the ortho and para positions, sev

Question

In the nitration of bromobenzene that leads to the ortho and para positions, several purification steps are performed. The dichloromethane layer is first washed with saturated aqueous sodium bicarbonate, then it is washed with saturated NaCl and then dried with sodium sulfate.

1. After the reaction has gone to completion, what is the purpose of adding saturated sodium bicarbonate to the reaction mixture?

-It is used to absorb excess heat generated by the exothermic reaction

-It causes excess bromine to be given off as a gas

-To neutralize any remaining acid

-To extract the bromonitrobenzene from the reaction mixture

2. After removing the dichrolomethane layer, why is it rinsed with saturated NaCl?

-To crystallize the bromonitrobenzene

-To remove any water soluble impurities from the dichloromethane layer

-It causes the bromonitrobenzene to precipitate out of solution

-It is used as the drying agent to remove any excess water

Explanation / Answer

1)

To neutralize any remaining acid

because nitration mixture is nothing bit concentrated H2SO4 and concentrated HNO3

bi carbonate will nuetralize this excess acid

2)

To remove any water soluble impurities from the dichloromethane layer

generally after separation organic layer will have some water if you treat that with sturated NaCl that will absorb that water als then followed by further treat ment with anhydrous MgSO4 .

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