Which of the following has the highest potential energy for pentane?

Options

A. anti conformation
B. eclipsed conformation
C. gauche conformation
D. all have same potential energy

Answer

To determine which conformation of pentane has the highest potential energy, we need to analyze the three types of conformations: anti, gauche, and eclipsed.

### Step-by-Step Solution:

1. **Understanding Pentane Structure**:
Pentane (C5H12) is a straight-chain alkane with five carbon atoms. Its molecular structure can be represented as CH3-CH2-CH2-CH2-CH3.

2. **Conformations of Pentane**:
The three main conformations of pentane are:
- **Eclipsed Conformation**: In this conformation, the hydrogen atoms on adjacent carbon atoms are aligned with each other. This results in maximum steric hindrance and torsional strain.
- **Gauche Conformation**: In this staggered conformation, the hydrogen atoms on adjacent carbons are positioned at a 60-degree angle to each other. This conformation has less steric hindrance than the eclipsed conformation.
- **Anti Conformation**: This is also a staggered conformation where the hydrogen atoms on adjacent carbons are positioned 180 degrees apart. This arrangement minimizes steric hindrance and is the most stable conformation.

3. **Potential Energy Analysis**:
- The **Eclipsed Conformation** has the highest potential energy due to the close proximity of hydrogen atoms, leading to increased repulsion and torsional strain.
- The **Gauche Conformation** has lower potential energy than the eclipsed conformation but higher than the anti conformation.
- The **Anti Conformation** has the lowest potential energy as it minimizes steric interactions.

4. **Conclusion**:
Therefore, among the three conformations of pentane, the **Eclipsed Conformation** has the highest potential energy.

### Final Answer:
The eclipsed conformation of pentane has the highest potential energy.

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