JEE Main · 2023 · 13 Apr 2023 · Shift 2 · Compounds Containing Nitrogen

The final product is 1,3,5-tribromobenzene, so the route must first install three bromine atoms and then remove a group that directs them. Reading the steps forward, \ce{Br2} in \ce{CS2} brominates the amine at its two ortho positions and the para position to give 2,4,6-tribromoaniline. Treatment with \ce{NaNO2}/HCl at low temperature diazotises the amino group, producing 2,4,6-tribromobenzenediazonium chloride. Warming this with hypophosphorous acid, \ce{H3PO2}, replaces the diazonium group by hydrogen, a deamination that furnishes 1,3,5-tribromobenzene. Since the amino group both fixes the 1,3,5 bromination pattern and is finally removed, compound A is aniline.