Evaluate the stereochemical and mechanistic rules regarding the addition of halogens () and hydrogen — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

A) True. The bridged halonium ion physically blocks front-side attack, forcing the halide nucleophile to attack from the back (anti-addition). B) False. Anti-addition of a symmetric reagent to a trans-alkene yields a meso compound (optically inactive due to internal symmetry), not a racemic mixture. (Cis-alkenes yield racemic mixtures). C) True. The Kharasch (peroxide) effect works only for $HBr$ because both propagation steps (radical addition to alkene and hydrogen abstraction from $HBr$) are exothermic. For $HCl$ and $HI$, one of the steps is highly endothermic, preventing the chain reaction. D) False. In the dark (absence of peroxides), $HBr$ follows electrophilic addition (Markovnikov's rule), yielding the more substituted product.