Which is an alicylic compound

Options

A. benzene
B. cyclo pentene
C. pyridine
D. pyrrole

Answer

To determine which of the given compounds is an alicyclic compound, we need to follow these steps:

### Step 1: Understand the Definition of Alicyclic Compounds
Alicyclic compounds are cyclic compounds that are non-aromatic and can be either saturated or unsaturated. They must satisfy the following conditions:
- They must be cyclic.
- They must be non-aromatic (not following Huckel's rule).
- They can be saturated (only single bonds) or unsaturated (contain double or triple bonds).

### Step 2: Analyze Each Compound
We will analyze the given compounds to see which one meets the criteria for being alicyclic.

1. **Benzene**:
- Structure: Benzene is a 6-membered ring with alternating double bonds.
- Aromaticity: It follows Huckel's rule (4n + 2 π electrons, where n = 1 gives 6 π electrons).
- Conclusion: Benzene is aromatic and therefore not alicyclic.

2. **Cyclopentene**:
- Structure: Cyclopentene is a 5-membered ring with one double bond.
- Aromaticity: It does not follow Huckel's rule as it has 4 π electrons (not of the form 4n + 2).
- Conclusion: Cyclopentene is non-aromatic and meets the criteria for being an alicyclic compound.

3. **Pyridine**:
- Structure: Pyridine is a 6-membered ring with one nitrogen atom.
- Aromaticity: It has 6 π electrons (follows Huckel's rule).
- Conclusion: Pyridine is aromatic and therefore not alicyclic.

4. **Pyrrole**:
- Structure: Pyrrole is a 5-membered ring with one nitrogen atom.
- Aromaticity: It has 6 π electrons (the lone pair of nitrogen participates in resonance).
- Conclusion: Pyrrole is aromatic and therefore not alicyclic.

### Step 3: Identify the Alicyclic Compound
From the analysis:
- **Benzene**: Aromatic
- **Cyclopentene**: Non-aromatic (Alicyclic)
- **Pyridine**: Aromatic
- **Pyrrole**: Aromatic

Thus, the only alicyclic compound among the options is **Cyclopentene**.

### Final Answer
**Cyclopentene is the alicyclic compound.**

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