## Step-by-Step Solution ### 1. **Identify the Bond of Rotation** The molecule shown is **2-butanol** (`CH3-CH(OH)-CH2-CH3`). You are to draw Newman projections **rotating around the C–C3 bond** (the carbon with the OH and the adjacent carbon). --- ### 2. **Assign Groups on Each Carbon** - **Front Carbon (C2):** - OH - H - CH3 - **Back Carbon (C3):** - H - CH2CH3 (ethyl) - H --- ### 3. **Draw All Newman Projections** There are **three key staggered** and **three key eclipsed** conformations (every 60° rotation): #### **A. Staggered Conformations (lowest energy)** 1. **Anti (OH & CH2CH3 opposite)** - Front: OH up, CH3 left, H right - Back: CH2CH3 down, H left, H right 2. **Gauche 1 (OH & CH2CH3 60° apart)** - OH gauche to CH2CH3 3. **Gauche 2 (OH & CH3 60° apart)** - OH gauche to CH3 #### **B. Eclipsed Conformations (highest energy)** 1. **Eclipsed 1 (OH & H)** - OH eclipses H 2. **Eclipsed 2 (OH & CH2CH3)** - OH eclipses CH2CH3 (highest energy) 3. **Eclipsed 3 (OH & H)** - OH eclipses other H --- ### 4. **Draw the Newman Projections** #### **Staggered (60° apart)** ``` View down C2–C3 bond (C2 front, C3 back): 1. Anti: H | OH-C-CH3 | CH2CH3 [Newman: OH (up), CH3 (left), H (right) // CH2CH3 (down), H (left), H (right)] 2. Gauche: - OH and CH2CH3 60° apart - OH (up), CH3 (left), H (right) // H (down), CH2CH3 (left), H (right) - OH (up), CH3 (left), H (right) // H (down), H (left), CH2CH3 (right) #### **Eclipsed (°, 120°, 240°)** - OH directly aligned with one of the back groups (H or CH2CH3). --- ### 5. **Energy Diagram Explanation** - **Anti** (OH and CH2CH3 opposite): **Lowest energy** (most stable, least steric hindrance) - **Gauche** (OH next to CH2CH3): **Higher energy** (steric hindrance between large groups) - **Eclipsed**: **Highest energy** (especially when OH and CH2CH3 overlap) --- ### 6. **Energy Diagram** ```plaintext Energy | | eclipsed | /\ | / \ | / \ eclipsed | / \ /\ | / \ / \ |____/____/\____/____\_____ Rotation (-360°) anti gauche eclipsed ``` - **Anti**: Lowest point - **Gauche**: Intermediate peaks - **Eclipsed**: Highest peaks (especially when OH and CH2CH3 overlap) --- ## **Summary Table** | Conformation | Groups Aligned | Relative Energy | |--------------|---------------|---------------------| | Anti | OH // CH2CH3 | Lowest | | Gauche | OH ~ CH2CH3 | Medium | | Eclipsed | OH // CH2CH3 | Highest (steric) | | Eclipsed | OH // H | High | --- ## **Final Answer** **Draw all six Newman projections** (three staggered, three eclipsed) for rotation about the C2–C3 bond. **Energy is lowest in the anti conformation** (OH and CH2CH3 opposite), **highest when OH and CH2CH3 eclipse**. **Energy diagram** shows alternating peaks (eclipsed) and valleys (staggered), with anti as the lowest valley. --- ### **Example Newman Projection (Anti)**  *Alt: Newman projection of 2-butanol showing anti conformation (OH and ethyl opposite)* --- If you need all Newman projections drawn out, let me know!