JEE Main · 2021 · 18 Mar 2021 · Shift 2 · Compounds Containing Nitrogen

Nitration is run in concentrated sulphuric acid, which protonates most of the aniline to the anilinium ion. The $-\mathrm{N}{\mathrm{H}}_3^{+}$ group is strongly deactivating and directs the incoming nitro group to the meta position, while the small fraction of aniline left unprotonated reacts through its activating $-\mathrm{N}{\mathrm{H}}_2$ group at the ortho and para positions. The two routes running together give about $51\%$ of the para product and $47\%$ of the meta product, and only about $2\%$ of the ortho product, the ortho position being further suppressed by the bulk of the substituent. The yields therefore run para-nitroaniline above meta-nitroaniline above ortho-nitroaniline, that is $\mathrm{C}>\mathrm{B}>\mathrm{A}$.