When *trans*-1-chloro-2-isopropylcyclohexane is subjected to rigid E2 elimination conditions using s — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

For a concerted E2 elimination in a constrained cyclohexane ring, both the departing leaving group (chlorine) and the abstracted $\beta$ -hydrogen must simultaneously occupy parallel axial positions to achieve the mandatory anti-periplanar transition state. In *trans*-1-chloro-2-isopropylcyclohexane, when the chlorine atom is positioned axially, the bulky trans-isopropyl group is physically forced into an adjacent equatorial position. The specific $\beta$ -carbon bearing this isopropyl group (C2) now has its single proton in an equatorial position, entirely preventing abstraction. Therefore, the base is kinetically forced to abstract the only available anti-periplanar axial proton from the adjacent C6 methylene carbon, strictly yielding 3-isopropylcyclohexene (the Hofmann product), completely bypassing Saytzeff thermodynamic controls.