# Step-by-Step Solution: Chair Conformations of trans-1,4-dibromocyclohexane ## 1. Understanding the Problem - **Compound:** trans-1,4-dibromocyclohexane - **Goal:** Draw the two most stable chair conformations and distinguish between them. ## 2. Cyclohexane Chair Basics - Cyclohexane rings adopt a **chair conformation** to minimize strain. - Each carbon has one **axial** (vertical) and one **equatorial** (slanted) position. - Substituents prefer **equatorial** positions to reduce 1,3-diaxial interactions (steric strain). ## 3. Structure of trans-1,4-dibromocyclohexane - "1,4" indicates bromines are on carbons 1 and 4. - "trans" means the bromines are on **opposite sides** of the ring (one up, one down). ## 4. Step-by-Step Drawing and Explanation ### **Chair Conformation #1** #### Step 1: Draw the Cyclohexane Chair - Number the carbons clockwise. - Place Br on C1 **axial up**. - Place Br on C4 **axial down**. - This satisfies the trans requirement (opposite faces). **Visual:** ``` Br (axial up) | / \ / \ | | \ / \ / Br (axial down) ``` *Image alt text: Chair cyclohexane with Br on C1 axial up and Br on C4 axial down* #### Step 2: Evaluate Stability - Both Br atoms are **axial** → strong 1,3-diaxial repulsions. - **Less stable** than if one or both Br are equatorial. --- ### **Chair Conformation #2 (Chair Flip)** #### Step 1: Flip the Chair - Chair flip swaps axial and equatorial positions. - Br on C1 moves from **axial up** to **equatorial up**. - Br on C4 moves from **axial down** to **equatorial down**. - Still on opposite faces (trans). **Visual:** ``` Br (equatorial up) / / \ / \ | | \ / \ / Br (equatorial down) ``` *Image alt text: Chair cyclohexane with Br on C1 equatorial up and Br on C4 equatorial down* #### Step 2: Evaluate Stability - Both Br atoms are **equatorial** → minimized steric strain. - **Most stable conformation**. --- ## 5. Summary Table | Conformation | Br1 | Br4 | Stability | |--------------|-----|-----|-------------------| | Chair #1 | axial up | axial down | Least stable | | Chair #2 | equatorial up | equatorial down | **Most stable** | ## 6. Final Answers **The two drawn conformations are:** 1. Both Br axial (least stable) 2. Both Br equatorial (most stable) **In trans-1,4-dibromocyclohexane, the most stable chair conformation is the one in which both bromine atoms occupy equatorial positions.** --- **Key Point:** _A chair flip interconverts these conformations, swapping axial and equatorial positions for every substituent._

# Conformational Analysis of trans-1,4-dibromocyclohexane ## 1. Problem Overview - **Compound:** trans-1,4-dibromocyclohexane - **Objective:** Draw and analyze the two most stable chair conformations. ## 2. Chair Conformation Basics - Cyclohexane can exist in a **chair conformation** to minimize strain. - Each carbon in the ring has: - One **axial** position (vertical) - One **equatorial** position (slanted) ## 3. Structure of trans-1,4-dibromocyclohexane - The **trans** configuration implies that the bromine substituents on carbons 1 and 4 are on **opposite sides** of the ring. ## 4. Drawing the Conformations ### **Chair Conformation #1: Axial Bromines** 1. **Draw the Cyclohexane Chair:** - Number the carbons from 1 to 6 in a clockwise direction. - Place Br on C1 in the **axial up** position. - Place Br on C4 in the **axial down** position. **Visual:** ``` Br (axial up) | / \ / \ | | \ / \ / Br (axial down) ``` *Image alt text: Cyclohexane chair conformation with Br on C1 axial up and Br on C4 axial down.* 2. **Stability Evaluation:** - Both bromine atoms are in **axial** positions, leading to significant **1,3-diaxial interactions**. - This conformation is **less stable** due to steric strain. --- ### **Chair Conformation #2: Equatorial Bromines** 1. **Flip the Chair:** - Swap axial and equatorial positions from the first conformation. - Br on C1 moves to **equatorial up**. - Br on C4 moves to **equatorial down**. **Visual:** ``` Br (equatorial up) / / \ / \ | | \ / \ / Br (equatorial down) ``` *Image alt text: Cyclohexane chair conformation with Br on C1 equatorial up and Br on C4 equatorial down.* 2. **Stability Evaluation:** - Both bromine atoms are now in **equatorial** positions, minimizing steric strain. - This conformation is the **most stable**. --- ## 5. Summary of Conformations | Conformation | Br1 Position | Br4 Position | Stability | |--------------|--------------|--------------|-------------------| | Chair #1 | Axial Up | Axial Down | Least Stable | | Chair #2 | Equatorial Up| Equatorial Down | **Most Stable** | ## 6. Conclusion **Most Stable Conformation:** The conformation where both bromine atoms are in equatorial positions (Chair #2) is the most stable due to reduced steric strain. --- **Final Answer to Stability Question:** **The more stable conformation is the one with both bromines in equatorial positions.**

# Conformational Analysis of trans-1,4-dibromocyclohexane ## 1. Problem Overview - **Compound:** trans-1,4-dibromocyclohexane - **Objective:** Draw and analyze the two most stable chair conformations. ## 2. Chair Conformation Basics - Cyclohexane can exist in a **chair conformation** to minimize strain. - Each carbon in the ring has: - One **axial** position (vertical) - One **equatorial** position (slanted) ## 3. Structure of trans-1,4-dibromocyclohexane - The **trans** configuration implies that the bromine substituents on carbons 1 and 4 are on **opposite sides** of the ring. ## 4. Drawing the Conformations ### **Chair Conformation #1: Axial Bromines** 1. **Draw the Cyclohexane Chair:** - Number the carbons from 1 to 6 in a clockwise direction. - Place Br on C1 in the **axial up** position. - Place Br on C4 in the **axial down** position. **Visual:** ``` Br (axial up) | / \ / \ | | \ / \ / Br (axial down) ``` *Image alt text: Cyclohexane chair conformation with Br on C1 axial up and Br on C4 axial down.* 2. **Stability Evaluation:** - Both bromine atoms are in **axial** positions, leading to significant **1,3-diaxial interactions**. - This conformation is **less stable** due to steric strain. --- ### **Chair Conformation #2: Equatorial Bromines** 1. **Flip the Chair:** - Swap axial and equatorial positions from the first conformation. - Br on C1 moves to **equatorial up**. - Br on C4 moves to **equatorial down**. **Visual:** ``` Br (equatorial up) / / \ / \ | | \ / \ / Br (equatorial down) ``` *Image alt text: Cyclohexane chair conformation with Br on C1 equatorial up and Br on C4 equatorial down.* 2. **Stability Evaluation:** - Both bromine atoms are now in **equatorial** positions, minimizing steric strain. - This conformation is the **most stable**. --- ## 5. Summary of Conformations | Conformation | Br1 Position | Br4 Position | Stability | |--------------|--------------|--------------|-------------------| | Chair #1 | Axial Up | Axial Down | Least Stable | | Chair #2 | Equatorial Up| Equatorial Down | **Most Stable** | ## 6. Conclusion **Most Stable Conformation:** The conformation where both bromine atoms are in equatorial positions (Chair #2) is the most stable due to reduced steric strain. --- **Final Answer to Stability Question:** **The more stable conformation is the one with both bromines in equatorial positions.**