# Step-by-Step Solution: Skeletal Structure of **cis-1,3-dimethylcyclohexane** ## 1. **Understand the Name** - **Cyclohexane:** A six-membered carbon ring. - **1,3-dimethyl:** Two methyl (–CH₃) groups attached to carbons 1 and 3. - **cis:** Both methyl groups are on the **same side** of the ring plane (both "up" or both "down"). --- ## 2. **Draw the Cyclohexane Skeleton** Draw a simple hexagon to represent cyclohexane. Number the carbons: ``` 1 / \ 6 2 | | 5 3 \ / 4 ``` --- ## 3. **Add Methyl Groups at 1 and 3** - Attach **CH₃** groups to carbons 1 and 3. --- ## 4. **Apply the 'cis' Stereochemistry** - Both methyl groups should be either **both wedged** (pointing up) or **both dashed** (pointing down). - For skeletal structures, you can use lines above or below the ring to show "up" or "down." --- ## 5. **Draw the Skeletal Structure** ### **Chair Conformation (most accurate for cyclohexane):** Below is a simplified chair conformation with both methyls "up" (axial or equatorial depending on convention): ``` CH₃ | / \ / \ CH₃/ \ \ / \ / ``` Or, to show the cis relationship, draw both methyls as wedges (or both as dashes): ``` CH₃ | / \ / \ CH₃/ \ \ / \ / ``` *(Both methyls above the plane)* --- ## 6. **Final Answer with Explanation** - **cis-1,3-dimethylcyclohexane** has two methyl groups on carbons 1 and 3, both on the same side of the ring. - In a chair conformation, this means both methyls are either both axial or both equatorial, but both pointing in the same direction (both "up" or both "down"). ### **Skeletal Structure (with stereochemistry):** ```plaintext CH₃ | / \ / \ CH₃/ \ \ / \ / ``` *Both methyl groups are on the same side (cis).* --- ## **Summary Table** | Position | Substituent | Stereochemistry | |----------|-------------|-----------------| | 1 | CH₃ | Up (or Down) | | 3 | CH₃ | Up (or Down) | --- ## **Key Points** - "cis" means both methyl groups are on the same side. - Draw the cyclohexane ring and add methyls to carbons 1 and 3, both either up or both down. --- **Image Example:**  *cis-1,3-dimethylcyclohexane in a chair conformation, both methyl groups on the same side (up)* --- **Final Answer:** *The skeletal structure of cis-1,3-dimethylcyclohexane is a cyclohexane ring with methyl groups at carbons 1 and 3, both on the same side (both wedges or both dashes in a chair conformation).*