Which of the following is a biradical?

Options

A. Phenyl
B. Propenyl
C. Vinylidene
D. Ethylidene

Answer

To determine which of the given compounds is a biradical, we need to analyze each option and identify the presence of two independent radicals. A biradical is defined as a molecule that contains two unpaired electrons, typically located on different atoms.

### Step-by-Step Solution:

1. **Analyze the First Option: Phenyl**
- Draw the structure of phenyl (C6H5).
- Identify the position of the radical.
- Conclusion: Phenyl has only one radical. Therefore, it is **not** a biradical.

2. **Analyze the Second Option: Propionyl**
- Draw the structure of propionyl (C3H5O).
- Identify the position of the radical.
- Conclusion: Propionyl also has only one radical. Therefore, it is **not** a biradical.

3. **Analyze the Third Option: Vinylidiene**
- Draw the structure of vinylidiene (C2H2).
- Identify the presence of radicals after removing chlorine atoms (if applicable).
- Conclusion: Vinylidiene has two radicals formed from different carbon atoms. Therefore, it **is** a biradical.

4. **Analyze the Fourth Option: Ethylediene**
- Draw the structure of ethylediene (C2H4).
- Identify the presence of radicals.
- Conclusion: Ethylediene can produce two radicals, but they are not independent of each other. Therefore, it is **not** a biradical.

### Final Conclusion:
The correct answer is **Vinylidiene**, which is a biradical.

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