Flagpole intersection is present in:

Options

A. Boat form of cyclohexane
B. Chair form of cyclohexane
C. Anti form of n-butane
D. Fully eclipsed form of n-butane

Answer

To determine where flagpole interactions are present, we need to analyze the molecular structures of cyclohexene and n-butene, particularly focusing on their conformations. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Structures
- **Cyclohexene** can adopt different conformations, mainly the chair and boat forms.
- **n-Butene** can be represented using Newman projections to visualize its conformations.

**Hint:** Familiarize yourself with the basic structures of cyclohexene and n-butene, including their chair and boat forms.

### Step 2: Identify the Conformations
- **Chair Form of Cyclohexene:** In this conformation, the substituents are positioned to minimize steric hindrance, leading to a more stable structure.
- **Boat Form of Cyclohexene:** This conformation has two flagpole hydrogens that are positioned close to each other, which can lead to steric interactions.

**Hint:** Draw the chair and boat conformations of cyclohexene to visualize the positions of the substituents.

### Step 3: Analyze n-Butene
- **Newman Projections of n-Butene:** The fully eclipsed conformation shows the two methyl groups (CH3) directly behind each other, which leads to steric hindrance.
- The staggered conformation minimizes steric interactions, but it does not exhibit flagpole interactions.

**Hint:** Sketch the Newman projections for n-butene to understand the spatial arrangement of the groups.

### Step 4: Identify Flagpole Interactions
- **Flagpole Interactions:** These are specific interactions that occur in the boat form of cyclohexene where the two flagpole hydrogens (or larger groups, if substituted) are in close proximity, leading to steric hindrance.
- In the chair conformation, there are no flagpole interactions since the substituents are positioned to avoid such interactions.

**Hint:** Focus on the boat conformation of cyclohexene to identify where the flagpole interactions occur.

### Conclusion
The flagpole interactions are present in the **boat form of cyclohexene**. In contrast, n-butene does not exhibit flagpole interactions in its conformations.

**Final Answer:** Flagpole interactions are present in the boat form of cyclohexene.