Let's analyze **each structure** and the **factors** affecting their reaction rate with HCl. ## **Step 1: Understand the Reaction** **Alkenes react with HCl via electrophilic addition:** 1. The alkene π bond attacks H⁺ (from HCl), generating a carbocation intermediate. 2. Cl⁻ attacks the carbocation. **The rate-determining step** is the formation of the carbocation. The more stable the carbocation, the faster the reaction. --- ## **Step 2: Analyze Each Compound** ### **A: Cyclohexene** - No electron-withdrawing or donating groups. - Forms a secondary carbocation. ### **B: 3-Cyclohexen-1-one** - The double bond is **conjugated with a carbonyl** (enone). - The carbonyl group is electron-withdrawing (**deactivates** the alkene). - Conjugation stabilizes the alkene but makes it less nucleophilic. ### **C: 3,4-Epoxycyclohex-1-ene** - Double bond **conjugated with an epoxide** (electron-withdrawing, deactivates alkene). ### **D: 2-Oxacyclohex-3-en-1-one** - Double bond conjugated with both **oxygen and carbonyl**. - Two electron-withdrawing groups = **even less reactive**. ### **E: 2,3-Epoxycyclohex-4-en-1-one** - Double bond conjugated with **epoxide and carbonyl**. - Strongly deactivated. --- ## **Step 3: Rank Electron-Withdrawing Effects** **Alkene reactivity decreases with more electron-withdrawing groups:** - **A:** No EWG (most reactive) - **B, C:** One EWG (carbonyl in B, epoxide in C) - **D, E:** Two EWGs (least reactive) But **carbonyls are stronger EWGs than epoxides**. So order is: - **A > C > B > D > E** --- ## **Step 4: Final Ranking** | Compound | Structure | Reactivity with HCl (Highest → Lowest) | |----------|---------------|----------------------------------------| | A | Cyclohexene | 1 (highest) | | C | Epoxide | 2 | | B | Enone | 3 | | D | Epoxy + ketone| 4 | | E | Epoxy + ketone| 5 (lowest) | **Final Answer:** \[ \boxed{A > C > B > D > E} \] --- ### **Summary Table** | Rank | Compound | Explanation | |------|----------|-----------------------------| | 1 | A | No electron-withdrawing group| | 2 | C | One epoxide (mild EWG) | | 3 | B | One carbonyl (strong EWG) | | 4 | D | Epoxide + carbonyl | | 5 | E | Epoxide + carbonyl | --- **Key Point:** The more electron-withdrawing groups (EWGs) conjugated to the alkene, the **slower** the rate of electrophilic addition, because the alkene is less nucleophilic. Carbonyl (C=O) is a stronger EWG than epoxide (O).