In the context of nucleophilic substitution reactions of alkyl halides, which of the following halog — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

The order of bond dissociation enthalpy for carbon-halogen bonds is $C-F > C-Cl > C-Br > C-I$. Because iodine is the largest halogen, the $C-I$ bond features the poorest orbital overlap (carbon's $2sp^3$ with iodine's $5p$), making it the weakest bond. Consequently, less activation energy is required to break it heterolytically, making the iodide ion ($I^-$) an excellent leaving group. This results in alkyl iodides being the most reactive alkyl halides in both $S_N1$ and $S_N2$ mechanisms.