Let's solve each part step-by-step, starting with **SA.5**. --- # SA.5: Newman Projections and Strain Energy Graphs Let's analyze the rotation around the indicated bond for each molecule. ## a) **Propane down C2–C3** **Structure**: CH₃–CH₂–CH₃ View down the C2–C3 bond. ### Substituents: - **Front carbon (C2):** H, H, CH₃ - **Back carbon (C3):** H, H, CH₃ ### Newman Projections: As you rotate 360°, you get three unique staggered and three unique eclipsed conformations. **Staggered (most stable):** - Largest groups (CH₃) are anti (180° apart). **Eclipsed (least stable):** - Largest groups (CH₃) are eclipsed (° apart). ### Strain Energy vs. Angle Graph: - **Minima** at 60°, 180°, 300° (staggered) - **Maxima** at °, 120°, 240° (eclipsed) ``` Graph: Y-axis = Strain Energy, X-axis = Dihedral Angle (° to 360°) Periodic wave with 3 maxima (eclipsed) and 3 minima (staggered) ``` --- ## b) **2-methylbutane down C2–C3** **Structure:** CH₃–CH(CH₃)–CH₂–CH₃ View down C2–C3. ### Substituents: - **Front (C2):** H, CH₃, CH(CH₃) - **Back (C3):** H, CH₃, CH₂CH₃ ### Newman Projections: Draw projections for each 60° rotation: - Look for **gauche** and **anti** interactions. - Most stable: largest groups anti (CH(CH₃) vs CH₂CH₃). - Least stable: largest groups eclipsed. ### Strain Energy Graph: - Minima when large groups are anti. - Maxima when large groups are eclipsed. --- ## c) **2,3-dimethylbutane down C2–C3** **Structure:** CH₃–CH(CH₃)–CH(CH₃)–CH₃ View down C2–C3. ### Substituents: - **Front (C2):** H, CH₃, CH(CH₃) - **Back (C3):** H, CH₃, CH(CH₃) ### Newman Projections: - Most stable: methyl groups anti. - Least stable: methyl groups eclipsed. ### Strain Energy Graph: - Similar to part (b), but maxima and minima are more pronounced due to larger groups. --- # SA.6: Most and Least Stable Conformations For each molecule, **draw two Newman projections**: one for the most stable (staggered/anti, large groups apart) and one for the least stable (eclipsed, large groups together). For example: **a) 2-methylpentane down C3–C4** - **Most stable:** Large groups anti. - **Least stable:** Large groups eclipsed. Repeat this for each molecule (b)–(f), focusing on keeping the largest substituents as far apart as possible for the most stable conformation, and together (eclipsed) for the least stable. --- ## **Summary Table** | Molecule | Most Stable (anti) | Least Stable (eclipsed) | |----------|---------------------|-------------------------| | a | Large groups anti | Large groups eclipsed | | b | "" | "" | | ... | "" | "" | --- ## **Final Notes:** - **Draw all Newman projections for each 60° rotation**. - **Energy graph:** Minima = staggered/anti, Maxima = eclipsed. - **Stability:** Staggered/anti = most stable, Eclipsed = least stable. --- If you need the **actual drawn projections** for any part or a specific example in detail, let me know and I can provide the actual diagrams!