Which of the following rigorous thermodynamic and kinetic statements absolutely accurately character — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

A) True. The E1 mechanism specifically features a slow, unimolecular ionization step to form a carbocation. C) True. This exact same carbocation is the shared intermediate for the $S_N1$ pathway, making them inherent, unavoidable competitors. D) True. Because the $\beta$ -proton is lost in the second, extremely fast step, substituting it with heavy deuterium does not noticeably alter the overall activation energy, meaning no primary isotope effect is observed ($k_H/k_D \approx 1$). Option (B) is false; while the thermodynamically more stable *trans* (or *E*) isomer is heavily favored, the *cis* (or *Z*) isomer is invariably still formed in minor amounts because rapid rotation around the single bond in the carbocation allows for multiple elimination geometries.