During the classical solvolysis of *tert*-butyl bromide in hot aqueous ethanol, both substitution () — Haloalkanes and Haloarenes Chemistry Question
Question
During the classical solvolysis of *tert*-butyl bromide in hot aqueous ethanol, both substitution ($S_N1$) and elimination ($E1$) products are isolated. If the identity of the halogen leaving group is deliberately changed from bromide to iodide, what is the expected critical impact on the relative ratio of the resulting $S_N1$ to $E1$ products, assuming all other conditions remain perfectly constant?
💡 Solution & Explanation
The critical cleavage of the carbon-halogen bond constitutes the first, rate-determining step shared by both the $E1$ and $S_N1$ mechanisms. Once this difficult step is fully complete, the leaving group (whether it was bromide or iodide) has cleanly departed and the identical *tert*-butyl carbocation intermediate is formed. The branching between substitution and elimination occurs exclusively in the second step. Because the identical isolated carbocation is formed regardless of the initial leaving group's identity, the relative ratio of substitution to elimination products depends purely on the solvent environment and the carbocation's structure, completely independent of the departed halogen.