Which of the following statements rigorously describe the fundamental properties of the arenium ion — Haloalkanes and Haloarenes Chemistry Question
Question
Which of the following statements rigorously describe the fundamental properties of the arenium ion (sigma complex) intermediate formed during the direct electrophilic halogenation of benzene?
💡 Solution & Explanation
A) True. Drawing the resonance structures of the sigma complex shows the positive charge localizes only on the carbons ortho and para to the $sp^3$ carbon. B) False. The formation of the $sp^3$ carbon breaks the continuous cyclic loop of p-orbitals, causing a temporary but complete loss of aromaticity and its associated stabilization energy. C) True. The carbon bonded to the electrophile forms a fourth sigma bond, rehybridizing from planar $sp^2$ to tetrahedral $sp^3$. D) True. Overcoming the loss of aromaticity requires a massive energy input, making the formation of this intermediate the slow, rate-determining step.