Which of the following is an isomeric pair?

Options

A. Ethane and propane
B. Ethane and ethene
C. Propane and butane
D. Butane and 2-methylpropane

Explanation

To determine which of the given options is an isomeric pair, we need to identify compounds that have the same molecular formula but different structural formulas. Let's analyze the compounds mentioned in the video transcript step by step.

### Step 1: Identify the Compounds and Their Molecular Formulas

1. **Ethane (C2H6)**:
- Structure: CH3-CH3
- Molecular Formula: C2H6

2. **Propane (C3H8)**:
- Structure: CH3-CH2-CH3
- Molecular Formula: C3H8

3. **Ethene (C2H4)**:
- Structure: CH2=CH2
- Molecular Formula: C2H4

4. **Butane (C4H10)**:
- Structure: CH3-CH2-CH2-CH3
- Molecular Formula: C4H10

5. **2-Methylpropane (C5H12)**:
- Structure: (CH3)2CH-CH3
- Molecular Formula: C5H12

### Step 2: Compare Molecular Formulas

- **Ethane (C2H6)** and **Propane (C3H8)**: Different molecular formulas (C2H6 vs. C3H8).
- **Ethane (C2H6)** and **Ethene (C2H4)**: Different molecular formulas (C2H6 vs. C2H4).
- **Propane (C3H8)** and **Butane (C4H10)**: Different molecular formulas (C3H8 vs. C4H10).
- **Butane (C4H10)** and **2-Methylpropane (C5H12)**: Different molecular formulas (C4H10 vs. C5H12).
- **Butane (C4H10)** and **2-Methylpropane (C5H12)**: Different molecular formulas (C4H10 vs. C5H12).

### Step 3: Identify Isomeric Pair

Now, let's look for isomers. Isomers must have the same molecular formula:

- **Butane (C4H10)** and **2-Methylpropane (C4H10)**: Both have the same molecular formula (C4H10) but different structures.

### Conclusion

The isomeric pair is **Butane (C4H10)** and **2-Methylpropane (C4H10)**.