Why is NH2 group of aniline acetylated before carrying out nitration?
To obtain p-Nitroaniline as the major product.
Direct nitration of Aniline yields tarry oxidation products and nitro derivatives compounds. In acidic medium, aniline is protonated, results in the formation of anilinium ion which is meta-directing. Thus, ortho-, para- and meta-Nitroaniline compounds are formed. 51% of the total products is p-Nitroaniline, 47% m-Nitroaniline and 2% o-Nitroaniline.
To control the nitration reaction and tarry oxidation products and nitro derivatives products formation, the NH2 group of aniline is acetylated before carrying out nitration. Here, the major product is p-Nitroaniline.
The amine group is protected by acetylation reaction with acetic anhydride.
