NEET 2023, Chemistry Q16: Introduction to Mechanism of Organic Reaction

Step (i): Sandmeyer-type reaction with ${\text{Cu}}_2{\text{Br}}_2$/HBr replaces the diazonium group with bromine, giving bromobenzene (${\text{C}}_6{\text{H}}_5\text{Br}$).

Step (ii): Mg in dry ether inserts into the C–Br bond to form the Grignard reagent phenylmagnesium bromide (${\text{C}}_6{\text{H}}_5\text{MgBr}$).

Step (iii): Hydrolysis with water protonates the carbanion, replacing $-\text{MgBr}$ with $-\text{H}$ to yield benzene.