An organic chemist heats a sample of purely synthesized (bromomethyl)cyclopentane in heavily aqueous — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

The ionization of (bromomethyl)cyclopentane initially yields a highly unstable primary carbocation located strictly outside the ring: [$C_5H_9-CH_2^+$]. The five-membered ring possesses noticeable internal angle strain ($\approx 108^\circ$ compared to ideal $109.5^\circ$). To simultaneously alleviate this ring strain and convert the $1^\circ$ carbocation into a much more stable $2^\circ$ carbocation, a ring expansion vigorously occurs. One of the $C-C$ bonds within the cyclopentyl ring breaks and permanently attaches to the external positive $CH_2$ carbon, expanding the overall framework into a completely unstrained six-membered cyclohexyl carbocation. Water then traps this stable intermediate, yielding cyclohexanol. The final ring unequivocally contains 6 carbon atoms.