JEE Main · 2024 · 29 Jan 2024 · Shift 2 · Compounds Containing Nitrogen

Addition of HI to 4-methylcyclohex-1-ene follows Markovnikov's rule: protonation of the double bond generates the more stable (more substituted) carbocation at the ring carbon best able to stabilise positive charge, and iodide ion then attacks this carbon, giving 1-iodo-4-methylcyclohexane.

The other proposed reactions do not hold up. Treating a primary aliphatic amine with $\mathrm{HN}{\mathrm{O}}_2$ in water liberates ${\mathrm{N}}_2$ and gives the corresponding alcohol with water as the only other product — not HCl. Photochemical bromination under UV light proceeds by a free-radical chain substitution at a C–H bond, not the vicinal-addition product shown. Hofmann bromamide degradation of ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{CON}{\mathrm{H}}_2$ (propanamide) removes the carbonyl carbon as carbonate, so the resulting amine has one carbon fewer than the amide; the product written retains all three carbons, which the reaction does not give.

The Markovnikov addition of HI to 4-methylcyclohex-1-ene is the correct reaction.