Identify Alkene Structure from Ozonolysis Products

To identify the structure of the alkene $(X)$, we analyze the products obtained from its reductive ozonolysis $(\text{O}_3 / \text{Zn}, \text{H}_2\text{O})$ by working backward and reconstructing the parent carbon skeleton.

---

1. Analysis of the Products

1. Formaldehyde ($2\text{ moles of } \text{HCHO}$): $\text{H}_2\text{C=O}$ Each mole of formaldehyde ($\text{HCHO}$) is formed by the cleavage of an exocyclic terminal double bond ($=\text{CH}_2$). Thus, the starting alkene $(X)$ contains two $=\text{CH}_2$ groups.

2. 2-Oxopropanedial ($1\text{ mole of } \text{H-C(=O)-C(=O)-C(=O)-H}$): $\text{O=CH}-\overset{\overset{\text{O}}{\parallel}}{\text{C}}-\text{CH=O}$

   • The two terminal aldehyde groups ($-\text{CHO}$) arise from the cleavage of endocyclic double bonds ($\text{C=C}$) in the ring.
   • The central carbonyl group ($-\text{C(=O)}-$) arises from a carbon atom that was originally attached to an exocyclic double bond ($=\text{CH}_2$). Upon ozonolysis, this exocyclic double bond cleaves to yield a ketone carbonyl at this position and $1\text{ mole of } \text{HCHO}$.

3. Butane-2,3-dione ($1\text{ mole of } \text{CH}_3\text{-C(=O)-C(=O)-CH}_3$): $\text{CH}_3-\overset{\overset{\text{O}}{\parallel}}{\text{C}}-\overset{\overset{\text{O}}{\parallel}}{\text{C}}-\text{CH}_3$

   • This fragment contains two acetyl groups ($\text{CH}_3-\text{C(=O)}-$) linked by a single carbon-carbon bond ($\text{C}-\text{C}$).
   • The two carbonyl carbons correspond to ring carbons that were each attached to a methyl group ($-\text{CH}_3$) and participated in double bonds.

---

2. Reconstructing the Alkene $(X)$

To find the structure of alkene $(X)$, we replace each carbonyl oxygen ($=\text{O}$) in the products with a double bond ($\text{C=C}$) connecting the corresponding carbon atoms:

• Joining the two terminal aldehyde carbons of $\text{OHC}-\text{CO}-\text{CHO}$ with the carbonyl carbons of $\text{CH}_3-\text{CO}-\text{CO}-\text{CH}_3$ re-establishes the six-membered ring.
• Restoring the exocyclic double bonds ($=\text{CH}_2$) at the central carbonyl carbon of the tri-carbonyl fragment and at the acetyl carbons accounts for all $2\text{ moles of } \text{HCHO}$.

This connectivity corresponds precisely to the structure shown in Option D.

---

Conclusion

The correct option is D.