The aromatic compound would be

Options

A.
B.
C.
D.

Answer

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

### Step 1: Identify the Compounds
We have four compounds to analyze. Let's denote them as Compound A, Compound B, Compound C, and Compound D.

### Step 2: Apply Aromaticity Criteria
To be classified as aromatic, a compound must satisfy the following criteria:
1. It must be cyclic.
2. It must be planar.
3. It must have a conjugated system of π electrons.
4. It must follow Hückel's rule, which states that it should have \(4n + 2\) π electrons, where \(n\) is a non-negative integer.

### Step 3: Analyze Each Compound

#### Compound A
- **Structure**: Contains a nitrogen atom with a lone pair.
- **Analysis**: The lone pair can participate in conjugation, leading to a total of 8 π electrons (4n, where n=2). This means it is anti-aromatic, thus **not aromatic**.

#### Compound B
- **Structure**: Similar to Compound A but contains boron.
- **Analysis**: The presence of boron (which has a vacant p orbital) does not allow for a complete conjugation system, and the structure is disrupted by sp³ hybridized carbon. Therefore, it is **not aromatic**.

#### Compound C
- **Structure**: Contains a negative charge.
- **Analysis**: The negative charge contributes to the π electron count, leading to a total of 8 π electrons (again, 4n). Thus, it is also **not aromatic**.

#### Compound D
- **Structure**: Contains a complete cyclic structure with 6 π electrons.
- **Analysis**: This compound has 6 π electrons, which fits Hückel's rule (4n + 2, where n=1). Additionally, it has a planar structure and a conjugated system. Therefore, it is **aromatic**.

### Conclusion
The aromatic compound among the given options is **Compound D**.

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