KCET 2026 Chemistry Solved Paper

Concept:In strong acidic medium, aniline is protonated to the anilinium ion, which is meta-directing.Explanation:The amino group $-\mathrm{NH}_{2}$ normally increases electron density on the benzene ring by resonance.Therefore, under ordinary conditions, it is ortho and para directing.Nitration is carried out using concentrated $\mathrm{HNO}_{3}$ and concentrated $\mathrm{H}_{2}\mathrm{SO}_{4}$.In this strongly acidic medium, the lone pair on nitrogen accepts a proton:$$\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{NH}_{2} + \mathrm{H}^{+} \rightarrow \mathrm{C}_{6}\mathrm{H}_{5}\mathrm{NH}_{3}^{+}$$So aniline is converted into the anilinium ion, $\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{NH}_{3}^{+}$.The group $-\mathrm{NH}_{3}^{+}$ is electron-withdrawing and directs incoming electrophiles to the meta position.Hence, nitration of aniline in strong acidic medium gives a significant amount of m-nitroaniline.The other options are incorrect because $-\mathrm{NH}_{2}$ is not meta-directing under normal conditions, and molar mass is not a factor in this reaction.Answer:Option B: In strong acidic medium, aniline is present as anilinium ion.