Which of the following is an aromatic compound

Options

A. Phenol
B. Naphthalene
C. Pyridine
D. All

Answer

To determine which of the given compounds is aromatic, we will follow these steps:

### Step 1: Understand Huckel's Rule
Aromatic compounds must satisfy Huckel's rule, which states that a compound is aromatic if it has \(4n + 2\) π electrons, where \(n\) is a non-negative integer (0, 1, 2, ...).

### Step 2: Analyze Each Compound
We will analyze the given compounds one by one to count the number of π electrons.

#### Compound A: Phenol
1. **Structure**: Phenol has a benzene ring with a hydroxyl group (-OH).
2. **Pi Bonds**: The benzene ring has 3 double bonds, contributing 6 π electrons (2 from each double bond).
3. **Huckel's Rule**:
- Set \(n = 1\): \(4(1) + 2 = 6\) π electrons.
- Conclusion: Phenol is aromatic.

#### Compound B: Naphthalene
1. **Structure**: Naphthalene consists of two fused benzene rings.
2. **Pi Bonds**: There are 5 double bonds, contributing 10 π electrons.
3. **Huckel's Rule**:
- Set \(n = 2\): \(4(2) + 2 = 10\) π electrons.
- Conclusion: Naphthalene is aromatic.

#### Compound C: Pyridine
1. **Structure**: Pyridine is a six-membered ring containing five carbon atoms and one nitrogen atom.
2. **Pi Bonds**: Pyridine has 3 double bonds, contributing 6 π electrons. The lone pair on nitrogen does not contribute to the π system as it is perpendicular to the ring.
3. **Huckel's Rule**:
- Set \(n = 1\): \(4(1) + 2 = 6\) π electrons.
- Conclusion: Pyridine is aromatic.

### Step 3: Conclusion
Since all three compounds (Phenol, Naphthalene, and Pyridine) satisfy Huckel's rule, they are all aromatic compounds. Therefore, the correct answer is:

**Option D: All of the above are aromatic compounds.**

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