Which of the following is an aromatic species ?

Options

A.
B.
C.
D. None of the above

Explanation

To determine which of the given species is aromatic, we need to follow a systematic approach based on the criteria for aromaticity. Here’s a step-by-step solution:

### Step 1: Understand the Criteria for Aromaticity
A compound is considered aromatic if it meets the following criteria:
1. **Planarity**: The molecule must be planar or nearly planar.
2. **Conjugation**: There must be a continuous overlap of p-orbitals, allowing for delocalization of π electrons.
3. **Hückel's Rule**: The molecule must have \(4n + 2\) π electrons, where \(n\) is a non-negative integer (0, 1, 2, ...).

### Step 2: Analyze Each Compound
Let’s analyze the given options one by one based on the criteria.

#### Compound A:
- **Planarity**: Check if the structure is planar.
- **Conjugation**: Identify if there is a continuous chain of p-orbitals. If there is a break in conjugation (e.g., an sp³ hybridized carbon), it cannot be aromatic.
- **Electron Count**: Count the number of π electrons. If the conjugation is broken, even if the count is \(4n + 2\), it will not be aromatic.

#### Conclusion for Compound A:
- If the conjugation is broken, it is non-aromatic despite having \(4n + 2\) electrons.

#### Compound B:
- **Planarity**: Check for planarity.
- **Conjugation**: Ensure that there is continuous conjugation without any breaks.
- **Electron Count**: Count the π electrons. If the total is \(4n + 2\), then it is aromatic.

#### Conclusion for Compound B:
- If it has continuous conjugation and \(6\) π electrons (which fits \(4n + 2\) for \(n=1\)), it is aromatic.

#### Compound C:
- **Planarity**: Check for planarity.
- **Conjugation**: Identify if there are breaks in conjugation.
- **Electron Count**: Count the π electrons. If the total is \(4n\) instead of \(4n + 2\), it indicates anti-aromaticity.

#### Conclusion for Compound C:
- If it has \(8\) π electrons (which fits \(4n\) for \(n=2\)), it is anti-aromatic and not aromatic.

### Final Decision:
Based on the analysis:
- **Compound A**: Non-aromatic.
- **Compound B**: Aromatic.
- **Compound C**: Anti-aromatic.

Thus, the aromatic species is **Compound B**.