The decreasing order of boiling points of the following alcohols is

Options

A. 3-methylbutan-2-ol `gt` 2 - methylbutan-2-ol `gt` pentan-1-ol
B. pentan-1-ol `gt` 3- methylbutan-2-ol
C. 2-methylbutan-2-ol `gt ` 3-methylbutan-2-ol `gt` pentan-1-ol
D. 2-methylbutan -2-ol `lt` pentan -1-ol `lt` 3-mehtylbutan-2-ol

Answer

To determine the decreasing order of boiling points of the given alcohols, we need to analyze the structures and the branching of each compound. The boiling point of alcohols is influenced by the strength of intermolecular forces, particularly hydrogen bonding, which is affected by the molecular structure and branching.

### Step-by-Step Solution:

1. **Identify the Structures of the Alcohols**:
- **3-Methylbutan-2-ol**: This compound has a branched structure.
- **2-Methylbutan-2-ol**: This compound is more branched than 3-methylbutan-2-ol.
- **Pentan-1-ol**: This compound is a straight-chain alcohol with no branching.

2. **Analyze the Effect of Branching on Boiling Points**:
- Alcohols with less branching tend to have higher boiling points due to a larger surface area, which allows for stronger van der Waals forces and better hydrogen bonding.
- Conversely, more branched alcohols have a smaller surface area, leading to weaker intermolecular forces and lower boiling points.

3. **Rank the Alcohols Based on Branching**:
- **Pentan-1-ol** (least branched) will have the highest boiling point.
- **3-Methylbutan-2-ol** (moderately branched) will have a lower boiling point than pentan-1-ol but higher than 2-methylbutan-2-ol.
- **2-Methylbutan-2-ol** (most branched) will have the lowest boiling point.

4. **Conclusion**:
- The decreasing order of boiling points is: **Pentan-1-ol > 3-Methylbutan-2-ol > 2-Methylbutan-2-ol**.

### Final Answer:
The correct order of boiling points from highest to lowest is:
**Pentan-1-ol > 3-Methylbutan-2-ol > 2-Methylbutan-2-ol**.

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