JEE Advanced 2024 Paper 2, Chemistry Section 1 Q3: Aromatic Hydrocarbons: Benzene

Step (i): Reduction of L-glucose ($C_6{H}_{12}{O}_6$) with HI under heat removes all hydroxyl groups and produces $n$-hexane, $C_6{H}_{14}$.

Step (ii): $n$-hexane on aromatisation over ${\text{Cr}}_2{\text{O}}_3$ at $775$ K and $10\text{–}20$ atm gives benzene by cyclisation and dehydrogenation. So intermediate $P$ is benzene.

Final step: Benzene treated with excess ${\text{Cl}}_2$ in the presence of UV light undergoes free-radical addition (not electrophilic substitution) across all three double bonds, giving $1,2,3,4,5,6$-hexachlorocyclohexane (commonly known as BHC or benzene hexachloride).

Hence the major product $Q$ is the fully saturated hexachlorocyclohexane shown in option (D).