Boiling point is highest for which compound?

Options

A. Pentane
B. 2-Methylbutane
C. 2, 2-dimethylpropane
D. 2-Methylpropane

Answer

To determine which compound has the highest boiling point among the given options, we need to analyze the structure of each compound and consider the factors that affect boiling points.

### Step-by-Step Solution:

1. **Identify the Compounds:**
- Option 1: Pentane (C5H12) - a straight-chain alkane.
- Option 2: 2-Methylbutane (C5H12) - a branched-chain alkane.
- Option 3: 2,2-Dimethylpropane (C5H12) - a branched-chain alkane.
- Option 4: 2-Methylpropane (C5H12) - a branched-chain alkane.

2. **Understand the Effect of Structure on Boiling Point:**
- Straight-chain alkanes generally have higher boiling points compared to their branched counterparts due to a larger surface area that allows for stronger Van der Waals forces (dispersion forces).
- The more branching present in a molecule, the lower the boiling point tends to be, as branching reduces the surface area available for intermolecular interactions.

3. **Compare the Structures:**
- Pentane is a straight-chain alkane with no branches.
- 2-Methylbutane has one branch.
- 2,2-Dimethylpropane has two branches.
- 2-Methylpropane has one branch.

4. **Analyze the Number of Carbon Atoms:**
- All compounds have the same number of carbon atoms (5), but the arrangement (straight vs. branched) affects the boiling point.

5. **Conclusion:**
- Since pentane is a straight-chain alkane and has no branches, it will have the highest boiling point among the given options due to greater surface area and stronger Van der Waals forces.

### Final Answer:
The compound with the highest boiling point is **Pentane (Option 1)**.