Both aliphatic and aromatic compounds are present in the pair

Options

A. benzene, phenol
B. isobutane, methane
C. ethane, methane
D. Isobutane, chlorobenzene

Explanation

To solve the question of identifying a pair of compounds that includes both aliphatic and aromatic compounds, we will analyze the given options step by step.

### Step 1: Understand the Definitions
- **Aliphatic Compounds**: These are compounds that consist of straight or branched chains of carbon atoms. They do not have a benzene ring and can be saturated (alkanes) or unsaturated (alkenes and alkynes).
- **Aromatic Compounds**: These compounds contain a benzene ring or similar structures that exhibit resonance. They are cyclic and have delocalized π-electrons.

### Step 2: Analyze Each Pair of Compounds
1. **Benzene and Phenol**:
- **Benzene**: An aromatic compound (C6H6) with a benzene ring.
- **Phenol**: Also an aromatic compound (C6H5OH) that contains a benzene ring.
- **Conclusion**: Both are aromatic. This pair does not satisfy the requirement.

2. **Isobutane and Methane**:
- **Isobutane**: An aliphatic compound (C4H10) with a branched chain.
- **Methane**: An open-chain compound (C1H4) and is not classified as either aromatic or aliphatic.
- **Conclusion**: This pair does not satisfy the requirement as methane is neither.

3. **Ethane and Methane**:
- **Ethane**: An aliphatic compound (C2H6) with a straight chain.
- **Methane**: An open-chain compound (C1H4) and is not classified as either aromatic or aliphatic.
- **Conclusion**: Both are aliphatic. This pair does not satisfy the requirement.

4. **Isobutane and Chlorobenzene**:
- **Isobutane**: An aliphatic compound (C4H10) with a branched chain.
- **Chlorobenzene**: An aromatic compound (C6H5Cl) that contains a benzene ring.
- **Conclusion**: This pair contains one aliphatic (isobutane) and one aromatic (chlorobenzene) compound. This pair satisfies the requirement.

### Final Answer
The correct pair that contains both aliphatic and aromatic compounds is **Isobutane and Chlorobenzene**.

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