Among these chain isomers are :
(I) `CH_(3)-CH_(3)-CH_(2)-CH_(2)-OH`
(II) `CH_(3)-CH_(2)-underset(OH)underset(|)(CH)-CH_(3)`
(III) `CH_(3)-underset(CH_(3))underset(|)overset(OH)overset(|)(C)-CH_(3)`

Options

A. I only
B. I and III
C. I and II
D. None of these

Answer

To determine which of the given compounds are chain isomers, we first need to understand what chain isomers are. Chain isomers are compounds that have the same molecular formula but differ in the arrangement of the carbon skeleton (i.e., the parent chain).

Let's analyze the given compounds step by step:

### Step 1: Identify the molecular formula of each compound.
1. **Compound I:** `CH₃-CH₃-CH₂-CH₂-OH`
- This compound has 4 carbon atoms (C) and 10 hydrogen atoms (H) plus one oxygen atom (O).
- Molecular formula: C₄H₁₀O

2. **Compound II:** `CH₃-CH₂-(OH)-(CH)-CH₃`
- This compound also has 4 carbon atoms and the same number of hydrogen and oxygen atoms.
- Molecular formula: C₄H₁₀O

3. **Compound III:** `CH₃-(CH₃)-(OH)-(C)-CH₃`
- This compound has 5 carbon atoms and the same number of hydrogen and oxygen atoms.
- Molecular formula: C₅H₁₂O

### Step 2: Analyze the structure of each compound.
- **Compound I** has a straight-chain structure with a hydroxyl (OH) group at the end of the chain.
- **Compound II** has a branched structure with the hydroxyl group on the second carbon.
- **Compound III** has a branched structure with a methyl group on the second carbon and a hydroxyl group.

### Step 3: Determine the type of isomerism.
- **Compound I and Compound II:** Both have the same molecular formula (C₄H₁₀O) but differ in the arrangement of the carbon skeleton. Thus, they are positional isomers, not chain isomers.
- **Compound II and Compound III:** These compounds have different molecular formulas (C₄H₁₀O for II and C₅H₁₂O for III). Therefore, they cannot be chain isomers.
- **Compound I and Compound III:** These compounds also have different molecular formulas (C₄H₁₀O for I and C₅H₁₂O for III), so they cannot be chain isomers either.

### Conclusion:
Based on the analysis, the only pair that can be considered chain isomers are the ones with the same molecular formula but different carbon skeletons. However, since none of the pairs fit this criterion, we conclude that:

- **There are no chain isomers among the given compounds.**