Which of the following pairs of compounds are chain isomers?

Options

A. n-Butyl alcohol and s-butyl alcohol
B. isobutyl alcohol and t-butyl alcohol
C. s-butyl alcohol and t-butyl alcohol
D. n-propyl alcohol and isompropyl alcohol

Explanation

To determine which pairs of compounds are chain isomers, we need to analyze the given options based on the structural differences in the carbon skeletons of the compounds. Chain isomers are compounds that have the same molecular formula but differ in the arrangement of the carbon chain.

### Step-by-Step Solution:

1. **Understand Chain Isomerism**:
- Chain isomerism occurs when compounds have the same molecular formula but differ in the branching of the carbon chain.

2. **Analyze Option A**:
- **Compounds**: Normal butyl alcohol (C4H10O) and secondary butyl alcohol (C4H10O).
- **Structures**:
- Normal butyl alcohol: CH3-CH2-CH2-CH2-OH
- Secondary butyl alcohol: CH3-CH(OH)-CH2-CH3
- **Conclusion**: The difference is in the position of the OH group, hence this is an example of position isomerism, **not chain isomerism**.

3. **Analyze Option B**:
- **Compounds**: Isobutyl alcohol (C4H10O) and tertiary butyl alcohol (C4H10O).
- **Structures**:
- Isobutyl alcohol: (CH3)2CH-CH2-OH
- Tertiary butyl alcohol: (CH3)3C-OH
- **Conclusion**: The OH group is in a different position, indicating position isomerism, **not chain isomerism**.

4. **Analyze Option C**:
- **Compounds**: Secondary butyl alcohol (C4H10O) and tertiary butyl alcohol (C4H10O).
- **Structures**:
- Secondary butyl alcohol: CH3-CH(OH)-CH2-CH3
- Tertiary butyl alcohol: (CH3)3C-OH
- **Conclusion**: The carbon skeleton changes (the branching of the carbon chain changes), indicating that this is an example of chain isomerism.

5. **Analyze Option D**:
- **Compounds**: N-propyl alcohol (C3H8O) and isopropyl alcohol (C3H8O).
- **Structures**:
- N-propyl alcohol: CH2-CH2-CH2-OH
- Isopropyl alcohol: CH3-CH(OH)-CH3
- **Conclusion**: The difference is in the position of the OH group, indicating position isomerism, **not chain isomerism**.

### Final Answer:
The pair of compounds that are chain isomers is **Option C** (secondary butyl alcohol and tertiary butyl alcohol).

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