Which of the following is aromatic hydrocarbon ?

Options

A.
B.
C.
D.

Answer

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

### Step 1: Understand Aromatic Hydrocarbons
Aromatic hydrocarbons are compounds that consist only of carbon and hydrogen atoms and have a specific structure that allows for delocalization of pi electrons. According to Huckel's rule, a compound is aromatic if it has a planar structure and contains a total of \(4n + 2\) pi electrons, where \(n\) is a non-negative integer (0, 1, 2, 3, ...).

### Step 2: Identify the Compounds
List the compounds provided in the question. For this example, let's assume we have the following compounds:
1. Benzene (C6H6)
2. Cyclohexene (C6H10)
3. Toluene (C7H8)
4. Aniline (C6H5NH2)

### Step 3: Check for Hydrocarbon Status
Aromatic hydrocarbons must consist only of carbon and hydrogen.
- Benzene: Yes, it is a hydrocarbon.
- Cyclohexene: Yes, it is a hydrocarbon.
- Toluene: Yes, it is a hydrocarbon.
- Aniline: No, it contains nitrogen, so it is not a hydrocarbon.

### Step 4: Count Pi Electrons
Next, we need to check the number of pi electrons in the remaining hydrocarbon compounds (Benzene, Cyclohexene, and Toluene).

1. **Benzene (C6H6)**:
- Structure: Benzene has 3 double bonds (6 pi electrons).
- Calculation: 3 double bonds × 2 electrons = 6 pi electrons.
- Check: \(4n + 2\) for \(n=1\) gives 6, so benzene is aromatic.

2. **Cyclohexene (C6H10)**:
- Structure: Cyclohexene has 1 double bond (2 pi electrons).
- Calculation: 1 double bond × 2 electrons = 2 pi electrons.
- Check: \(4n + 2\) for \(n=0\) gives 2, but cyclohexene is not planar and does not have the delocalization required for aromaticity.

3. **Toluene (C7H8)**:
- Structure: Toluene has 1 methyl group attached to a benzene ring, so it has 6 pi electrons from the benzene.
- Calculation: 6 pi electrons from the benzene structure.
- Check: \(4n + 2\) for \(n=1\) gives 6, so toluene is aromatic.

### Step 5: Conclusion
Based on the analysis, the aromatic hydrocarbons from the given options are Benzene and Toluene. However, if the question asks for only one answer, Toluene is a clear aromatic hydrocarbon because it is derived from benzene.

### Final Answer
**Toluene is an aromatic hydrocarbon.**