Which one of the following compound is not a planar ?

Options

A.
B.
C.
D.

Answer

To determine which of the given compounds is not planar, we need to analyze the nature of each compound based on their electronic structure and geometry. Here’s a step-by-step solution:

### Step 1: Understand Planarity in Compounds
Planarity in compounds is generally associated with aromatic and anti-aromatic compounds. Aromatic compounds are planar due to their cyclic structure and complete conjugation, while anti-aromatic compounds, although they have a cyclic structure, are unstable and can adopt non-planar conformations to minimize instability.

### Step 2: Identify the Compounds
Assuming we have four compounds to analyze, we will evaluate each one based on the criteria for aromaticity and planarity.

### Step 3: Analyze Each Compound
1. **Compound 1 (OxyPin)**:
- This compound has 8 π electrons (4n, where n=2).
- It is anti-aromatic and tends to adopt a non-planar (boat) conformation to avoid instability.
- **Conclusion**: This compound is **not planar**.

2. **Compound 2**:
- This compound has 6 π electrons (4n + 2, where n=1).
- It is aromatic and thus planar.
- **Conclusion**: This compound is **planar**.

3. **Compound 3**:
- This compound also has 6 π electrons (4n + 2, where n=1).
- It is aromatic and thus planar.
- **Conclusion**: This compound is **planar**.

4. **Compound 4**:
- This compound has 2 π electrons (4n, where n=0).
- It is also aromatic and thus planar.
- **Conclusion**: This compound is **planar**.

### Step 4: Final Conclusion
After analyzing all the compounds, we find that **Compound 1 (OxyPin)** is the only compound that is not planar due to its anti-aromatic nature, which forces it into a non-planar conformation.

### Answer
The compound that is **not planar** is **Compound 1 (OxyPin)**.

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