See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

**Step-by-step IUPAC Naming:** **1) Identify the parent structure:** The compound is a cyclobutane ring (4-membered ring), which is the parent chain. **2) Identify the substituents:** Two exocyclic double bonds ($C=C$) are attached to the ring, each bonded to a methyl group ($CH_3$). These are ethylidene groups ($=CH-CH_3$). **3) Number the ring positions:** Number the cyclobutane carbons to give the double bonds the lowest locants: - Position the first double bond at carbon 1 - Position the second double bond at carbon 4 - This gives positions **1 and 4** (not 2 and 4, or 1 and 3) **4) Determine the configuration:** Both exocyclic double bonds have the ethylidene groups in the **(E)-configuration** (the higher priority substituent points outward/away from the ring). **5) Construct the name:** - Locants: **1,4-** - Configuration: **[(E)-** - Substituent: **ethylidene]** - Parent: **cyclobutane** $$\boxed{\text{1,4-di-[(E)-ethylidene]cyclobutane}}$$ **Why C is correct:** The double bonds are at positions 1 and 4 (not 2,4 or 1,3), and both have **(E)-configuration** at the exocyclic double bonds. Option D omits "di-" and uses wrong nomenclature format.