JEE Main · 2024 · 30 Jan 2024 · Shift 2 · Compounds Containing Nitrogen

Benzene is nitrated with conc. ${\text{HNO}}_3$/conc. ${\text{H}}_2{\text{SO}}_4$ at 323–333 K to give nitrobenzene, which $\text{Sn/HCl}$ reduces to aniline — this is A. Aniline is diazotised with ${\text{NaNO}}_2$/HCl at 273–278 K to give the benzenediazonium salt, a stabilised electrophile. This diazonium ion couples with phenol, an electron-rich arene, at the position para to –OH (the most nucleophilic site on the phenoxide-like ring), giving the azo dye 4-hydroxyazobenzene — this is B. A is aniline and B is p-hydroxyazobenzene, ${\text{C}}_6{\text{H}}_5{\text{–N=N–C}}_6{\text{H}}_4\text{–OH}$.