# Step-by-Step Solution: Conformations of trans-1,4-dibromocyclohexane ## 1. Understanding the Molecule - **trans-1,4-dibromocyclohexane** means two Br atoms on carbon 1 and carbon 4 of cyclohexane, and they are trans to each other (one up, one down). - Cyclohexane can adopt two chair conformations by a **chair flip**. --- ## 2. Drawing the Two Chair Conformations ### **Chair Conformation 1** - Assign C1 as "up" and C4 as "down" (by convention). - Place Br on C1 **axial up**. - Place Br on C4 **axial down**. - All other positions are H. **Diagram Description:** ``` Br (axial up) | H — C1 C6 — H / \ H—C2 C5—H \ / H — C3 C4 — Br (axial down) ``` **(A simple annotated chair drawing would show Br's on C1 axial up, C4 axial down.)** --- ### **Chair Conformation 2 (After Chair Flip)** - All axial positions become equatorial, and vice versa. - After the flip, the Br on C1 moves to **equatorial up**. - The Br on C4 moves to **equatorial down**. **Diagram Description:** ``` Br (equatorial up) | H — C1 C6 — H / \ H—C2 C5—H \ / H — C3 C4 — Br (equatorial down) ``` --- ## 3. Comparing Stability - **Bulky groups (like Br) prefer equatorial positions** to reduce 1,3-diaxial interactions. - In the first chair: both Br atoms are axial (least stable). - In the second chair: both Br atoms are equatorial (most stable). --- ## 4. Final Answer ### **Most Stable Conformations:** - **Both Br atoms equatorial** (after chair flip): **most stable** - **Both Br atoms axial** (before chair flip): **less stable** **You can distinguish them based on whether the Br atoms are on axial or equatorial positions.** --- ### **Summary Table** | Conformation | C1 Br Position | C4 Br Position | Stability | |--------------|----------------|----------------|--------------| | 1 | Axial up | Axial down | Less stable | | 2 (flip) | Equatorial up | Equatorial down| Most stable | --- ## **Key Point** > **trans-1,4-dibromocyclohexane is most stable when both Br atoms occupy the equatorial positions (after a chair flip).** --- **[Image suggestion: Two chair conformations with Br atoms shown on axial and equatorial positions, labeled clearly. Alt text: "Two chair conformations of trans-1,4-dibromocyclohexane, with Br atoms on axial and equatorial positions."]**