See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Concept: E/Z isomerism requires assigning CIP priorities to the two substituents on each carbon of the C=C double bond. The E isomer has the two higher-priority groups on opposite sides of the double bond. General approach: For each option, assign CIP priorities to the substituents on each sp2 carbon, then determine whether the higher-priority groups are on opposite sides (E) or the same side (Z). Option (a): Left carbon: cyclobutene ring vs cyclohexyl. Right carbon: cyclopropene ring vs cyclohexyl. On the left carbon, the cyclobutene ring (contains a C=C, higher unsaturation, higher priority by phantom atoms rule) has higher priority than cyclohexyl. On the right carbon, cyclopropene (3-membered ring with double bond) vs cyclohexyl — cyclopropene has higher priority. Looking at the drawing, both higher-priority groups (cyclobutene on left, cyclopropene on right) appear to be on the same side (both above the main chain), making this Z. Additionally both cyclohexyl groups are on the same side below. Option (b): Left carbon has two heterocyclic rings containing P and S; right carbon has two heterocyclic rings containing O and S. Priority assignment: on the left carbon, the ring with P (atomic number 15) vs a ring with P — need to differentiate by ring size or substituents further. On the right carbon, S-containing rings compete. This is complex but the arrangement drawn places the 5-membered rings above and 6-membered rings below on both sides — same-side arrangement of same-sized rings suggests Z. Option (c): Left carbon: 5-membered dioxolane-type rings (with O atoms, atomic number 8). Right carbon: similar oxygen-containing rings. The arrangement shows both larger/higher-priority groups on the same side, suggesting Z configuration. Option (d): Left carbon bears two cyclopropane-derived substituents: a bicyclic/spiro cyclopropane (two cyclopropane rings fused, effectively higher priority due to more carbons at first point of difference) on the upper-left, and a cyclopropene on the lower-left. Right carbon bears a cyclopropene (upper-right, higher priority due to double bond phantom atoms giving higher CIP priority) and a cyclopropane-OH (lower-right, OH gives very high priority via oxygen). Assigning priorities: On the right carbon, cyclopropane-OH has higher priority (oxygen, atomic number 8 >> carbon). On the left carbon, the bicyclic spiro cyclopropane has higher priority than cyclopropene by CIP rules (more carbons at first shell or phantom atom comparison). In the drawing, the higher-priority group on the left carbon (bicyclic, upper-left) and the higher-priority group on the right carbon (cyclopropane-OH, lower-right) are on OPPOSITE sides of the double bond — this is the E configuration. Options (a), (b), and (c) have their respective higher-priority groups on the same side (Z). Only option (d) has the higher-priority substituents on opposite sides of the double bond. Therefore, the correct answer is D.