JEE Main · 2026 · 05 Apr 2026 · Shift 2 · Haloalkanes and Haloarenes

Ice-cold water hydrolyses the Grignard reagent, protonating the carbanion to the alkane $\mathrm{RH}$. One gram of this gas occupies $1.4\mathrm{d}{\mathrm{m}}^3$ at STP, so its molar mass is $\frac{22.4}{1.4}=16\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$, identifying it as methane and fixing $\mathrm{R}$ as the methyl group. Iodination of methane assisted by $\mathrm{HI}{\mathrm{O}}_3$ (which oxidises the liberated $\mathrm{HI}$ and drives the reaction forward) gives iodomethane, compound (X): $\mathrm{C}{\mathrm{H}}_4+{\mathrm{I}}_2\to \mathrm{C}{\mathrm{H}}_3\mathrm{I}+\mathrm{HI}$. Treating $\mathrm{C}{\mathrm{H}}_3\mathrm{I}$ with sodium in dry ether is a Wurtz coupling, $2\mathrm{C}{\mathrm{H}}_3\mathrm{I}+2\mathrm{Na}\to \mathrm{C}{\mathrm{H}}_3-\mathrm{C}{\mathrm{H}}_3+2\mathrm{NaI}$, so compound (Y) is ethane. The molar mass of ethane, ${\mathrm{C}}_2{\mathrm{H}}_6$, is $30\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$.