Lowest boiling point is for

Options

A. Butanol
B. Pentanol
C. 2-methyl propane -2-ol
D. 2-methyl butane-2-ol

Explanation

To determine which compound has the lowest boiling point among the given options, we will analyze the structures and the factors that affect boiling points.

### Step-by-Step Solution:

1. **Identify the Compounds:**
- Option A: Butanol (C4H10O)
- Option B: Pentanol (C5H12O)
- Option C: 2-Methylpropane-2-ol (C4H10O)
- Option D: 2-Methylbutane-2-ol (C5H12O)

2. **Understand the Factors Affecting Boiling Point:**
- Boiling point is influenced by the number of carbon atoms and the branching in the molecular structure.
- More carbon atoms generally lead to a higher boiling point due to increased surface area and stronger intermolecular forces.
- Increased branching in the carbon chain decreases the boiling point due to reduced surface area and weaker intermolecular forces.

3. **Analyze Each Compound:**
- **Butanol (Option A):**
- Straight-chain alcohol with 4 carbon atoms.
- Higher boiling point compared to branched isomers due to less branching.
- **Pentanol (Option B):**
- Straight-chain alcohol with 5 carbon atoms.
- Higher boiling point than butanol due to more carbon atoms.
- **2-Methylpropane-2-ol (Option C):**
- Has 4 carbon atoms but is branched.
- The branching will decrease the boiling point compared to straight-chain butanol.
- **2-Methylbutane-2-ol (Option D):**
- Has 5 carbon atoms and is branched.
- Higher boiling point than both butanol and 2-methylpropane-2-ol due to more carbon atoms.

4. **Comparison of Boiling Points:**
- Butanol (4 carbons, straight chain) > Pentanol (5 carbons, straight chain)
- 2-Methylpropane-2-ol (4 carbons, branched) < Butanol (due to branching)
- 2-Methylbutane-2-ol (5 carbons, branched) > 2-Methylpropane-2-ol (due to more carbon atoms)

5. **Conclusion:**
- Among the four compounds, **2-Methylpropane-2-ol (Option C)** has the lowest boiling point due to its branched structure and fewer carbon atoms compared to the other options.

### Final Answer:
**Option C: 2-Methylpropane-2-ol has the lowest boiling point.**