Which of the following is the pair of homocyclis & heterocyclic compound

Options

A. cyclopropane and cyclohexane
B. cycloethane and oxrane
C. pyridine and thiophene
D. cyclopentane and furane

Explanation

To determine the pair of homocyclic and heterocyclic compounds from the given options, we need to understand the definitions of these terms and analyze the compounds accordingly.

### Step-by-Step Solution:

1. **Define Homocyclic and Heterocyclic Compounds**:
- **Homocyclic Compounds**: These are cyclic compounds that contain only carbon atoms in the ring. All atoms in the ring are of the same type (carbon).
- **Heterocyclic Compounds**: These are cyclic compounds that contain at least one atom in the ring that is not carbon (such as nitrogen, oxygen, or sulfur).

2. **Analyze the Given Options**:
- **Option A: Cyclopropane and Cyclohexane**:
- Cyclopropane (C3H6) is a three-membered carbon ring.
- Cyclohexane (C6H12) is a six-membered carbon ring.
- Both compounds contain only carbon atoms, making them **homocyclic**.

- **Option B: Cycloethane and Oxirane**:
- Cycloethane does not exist as a stable compound (C2H4 cannot form a ring).
- Oxirane (C2H4O) contains an oxygen atom in the ring, making it **heterocyclic**.
- Since cycloethane does not exist, this option is invalid.

- **Option C: Pyridine and Thiophene**:
- Pyridine (C5H5N) has a nitrogen atom in the ring, making it **heterocyclic**.
- Thiophene (C4H4S) has a sulfur atom in the ring, also making it **heterocyclic**.
- Both compounds are heterocyclic, so this option does not contain a homocyclic compound.

- **Option D: Cyclopentane and Furan**:
- Cyclopentane (C5H10) is a five-membered carbon ring, making it **homocyclic**.
- Furan (C4H4O) contains an oxygen atom in the ring, making it **heterocyclic**.
- This option contains one homocyclic and one heterocyclic compound.

3. **Conclusion**:
- The correct answer is **Option D: Cyclopentane (homocyclic) and Furan (heterocyclic)**.

### Final Answer:
**Option D: Cyclopentane and Furan is the pair of homocyclic and heterocyclic compounds.**

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