Why the group of aniline acrylated before carrying out nitration ?
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Nitration is carried out by a mixture of conc HNO3 and conc H2SO4 called nitrating mixture. The mixture is a good oxidant.
The presence of NH2- group in aniline activates the ring by mesomeric effect. Consequently, the ring contains additional supply of electron. This makes the ring prone to attack by the oxidant.
Hence, when aniline is dirtectly treated with nitrating mixture causes ring destruction and nitration of aniline at ortho and para position does not yield good result.
To avoid this aniline is first acylated. This acyl group (CH3C=O) is a ring deactivating group and hence saves the ring from being destroyed by any oxidant like nitrating mixture. Hence, when aniline is acylated before nitration the probability of ring destruction by the nitrating mixture is minimised greatly and nitration of the aniline yields expected result.
This is why acylation of aniline is necessary before nitration.
The presence of NH2- group in aniline activates the ring by mesomeric effect. Consequently, the ring contains additional supply of electron. This makes the ring prone to attack by the oxidant.
Hence, when aniline is dirtectly treated with nitrating mixture causes ring destruction and nitration of aniline at ortho and para position does not yield good result.
To avoid this aniline is first acylated. This acyl group (CH3C=O) is a ring deactivating group and hence saves the ring from being destroyed by any oxidant like nitrating mixture. Hence, when aniline is acylated before nitration the probability of ring destruction by the nitrating mixture is minimised greatly and nitration of the aniline yields expected result.
This is why acylation of aniline is necessary before nitration.
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